diff --git a/example/example.pro b/example/example.pro
index b7e00c7..f56f194 100644
--- a/example/example.pro
+++ b/example/example.pro
@@ -7,6 +7,7 @@ SUBDIRS += linechart \
            percentbarchart \
            scatter \
            piechart \
+           piechartdrilldown \
            dynamiclinechart \
            axischart \
            multichart \
diff --git a/example/piechartdrilldown/main.cpp b/example/piechartdrilldown/main.cpp
new file mode 100644
index 0000000..4e82edc
--- /dev/null
+++ b/example/piechartdrilldown/main.cpp
@@ -0,0 +1,126 @@
+#include <QtGui/QApplication>
+#include <QMainWindow>
+#include <qchartglobal.h>
+#include <qchartview.h>
+#include <qpieseries.h>
+#include <qpieslice.h>
+#include <QTime>
+
+QTCOMMERCIALCHART_USE_NAMESPACE
+
+class DrilldownSlice : public QPieSlice
+{
+    Q_OBJECT
+
+public:
+    DrilldownSlice(qreal value, QString prefix, QSeries* drilldownSeries)
+        :m_drilldownSeries(drilldownSeries),
+        m_prefix(prefix)
+    {
+        setValue(value);
+        setLabelVisible(true);
+        updateLabel();
+        connect(this, SIGNAL(changed()), this, SLOT(updateLabel()));
+    }
+
+    QSeries* drilldownSeries() const { return m_drilldownSeries; }
+
+public Q_SLOTS:
+    void updateLabel()
+    {
+        QString label = m_prefix;
+        label += " - " + QString::number(this->value())+ "e (";
+        label += QString::number(this->percentage()*100, 'f', 1) + "%)";
+        qDebug() << "updateLabel" << label;
+        setLabel(label);
+    }
+
+private:
+    QSeries* m_drilldownSeries;
+    QString m_prefix;
+};
+
+class DrilldownChart : public QChartView
+{
+    Q_OBJECT
+public:
+    explicit DrilldownChart(QWidget *parent = 0):QChartView(parent), m_currentSeries(0) {}
+
+    void changeSeries(QSeries* series)
+    {
+        if (m_currentSeries)
+            removeSeries(m_currentSeries);
+        m_currentSeries = series;
+        addSeries(series);
+        setChartTitle(series->title());
+    }
+
+public Q_SLOTS:
+    void handleSliceClicked(QPieSlice* slice)
+    {
+        DrilldownSlice* drilldownSlice = static_cast<DrilldownSlice*>(slice);
+        changeSeries(drilldownSlice->drilldownSeries());
+    }
+
+private:
+    QSeries* m_currentSeries;
+};
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+
+    qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
+
+    QMainWindow window;
+
+    DrilldownChart* drilldownChart =  new DrilldownChart(&window);
+    drilldownChart->setRenderHint(QPainter::Antialiasing);
+    drilldownChart->setChartTheme(QChart::ChartThemeVanilla);
+
+    QPieSeries* yearSeries = new QPieSeries(drilldownChart);
+    yearSeries->setTitle("Sales by year - All");
+    yearSeries->setHoverHighlighting();
+
+    QList<QString> months;
+    months << "Jan" << "Feb" << "Mar" << "Apr" << "May" << "Jun" << "Jul" << "Aug" << "Sep" << "Oct" << "Nov" << "Dec";
+
+    int max = 1000;
+
+    QPieSeries* monthSeriesJane = new QPieSeries(drilldownChart);
+    monthSeriesJane->setTitle("Sales by month - Jane");
+    monthSeriesJane->setHoverHighlighting();
+    foreach (QString month, months)
+        *monthSeriesJane << new DrilldownSlice(qrand() % max, month, yearSeries);
+
+    QPieSeries* monthSeriesJohn = new QPieSeries(drilldownChart);
+    monthSeriesJohn->setTitle("Sales by month - John");
+    monthSeriesJohn->setHoverHighlighting();
+    foreach (QString month, months)
+        *monthSeriesJohn << new DrilldownSlice(qrand() % max, month, yearSeries);
+
+    QPieSeries* monthSeriesAxel = new QPieSeries(drilldownChart);
+    monthSeriesAxel->setTitle("Sales by month - Axel");
+    monthSeriesAxel->setHoverHighlighting();
+    foreach (QString month, months)
+        *monthSeriesAxel << new DrilldownSlice(qrand() % max, month, yearSeries);
+
+    *yearSeries << new DrilldownSlice(monthSeriesJane->total(), "Jane", monthSeriesJane);
+    *yearSeries << new DrilldownSlice(monthSeriesJohn->total(), "John", monthSeriesJohn);
+    *yearSeries << new DrilldownSlice(monthSeriesAxel->total(), "Axel", monthSeriesAxel);
+
+    QObject::connect(monthSeriesJane, SIGNAL(clicked(QPieSlice*)), drilldownChart, SLOT(handleSliceClicked(QPieSlice*)));
+    QObject::connect(monthSeriesJohn, SIGNAL(clicked(QPieSlice*)), drilldownChart, SLOT(handleSliceClicked(QPieSlice*)));
+    QObject::connect(monthSeriesAxel, SIGNAL(clicked(QPieSlice*)), drilldownChart, SLOT(handleSliceClicked(QPieSlice*)));
+    QObject::connect(yearSeries, SIGNAL(clicked(QPieSlice*)), drilldownChart, SLOT(handleSliceClicked(QPieSlice*)));
+
+    drilldownChart->changeSeries(yearSeries);
+
+    window.setCentralWidget(drilldownChart);
+    window.resize(600, 600);
+    window.show();
+
+    return a.exec();
+}
+
+#include "main.moc"
diff --git a/example/piechartdrilldown/piechartdrilldown.pro b/example/piechartdrilldown/piechartdrilldown.pro
new file mode 100644
index 0000000..df16e45
--- /dev/null
+++ b/example/piechartdrilldown/piechartdrilldown.pro
@@ -0,0 +1,9 @@
+!include( ../example.pri ) {
+ error( "Couldn't find the example.pri file!" )
+}
+TARGET = piechartdrilldown
+SOURCES += main.cpp
+HEADERS +=
+
+
+MOC_DIR = $$PWD/moc
diff --git a/src/piechart/qpieseries.cpp b/src/piechart/qpieseries.cpp
index 7749348..4e51234 100644
--- a/src/piechart/qpieseries.cpp
+++ b/src/piechart/qpieseries.cpp
@@ -188,6 +188,12 @@ void QPieSeries::add(QPieSlice* slice)
     add(QList<QPieSlice*>() << slice);
 }
 
+QPieSeries& QPieSeries::operator << (QPieSlice* slice)
+{
+    add(slice);
+    return *this;
+}
+
 
 /*!
     Adds a single slice to the series with give \a value and \a name.
@@ -348,10 +354,7 @@ void QPieSeries::setClickExplodes(bool enable)
     Convenience method for highlighting a slice when user hovers over the slice.
     It changes the slice color to be lighter and shows the label of the slice.
     Set \a enable to true to highlight a slice when user hovers on top of it.
-
-    \sa QPieSlice::isExploded(), QPieSlice::setExploded()
 */
-
 void QPieSeries::setHoverHighlighting(bool enable)
 {
     if (enable) {
@@ -364,6 +367,16 @@ void QPieSeries::setHoverHighlighting(bool enable)
 }
 
 /*!
+    Returns the sum of all slice values in this series.
+
+    \sa QPieSlice::value(), QPieSlice::setValue()
+*/
+qreal QPieSeries::total() const
+{
+    return m_total;
+}
+
+/*!
     \fn void QPieSeries::changed(const QPieSeries::ChangeSet& changeSet)
 
     This signal emitted when something has changed in the series.
@@ -456,7 +469,6 @@ void QPieSeries::highlightOn(QPieSlice* slice)
     Q_ASSERT(slice);
     QColor c = slice->brush().color().lighter();
     slice->setBrush(c);
-    slice->setLabelVisible(true);
 }
 
 void QPieSeries::highlightOff(QPieSlice* slice)
@@ -464,7 +476,6 @@ void QPieSeries::highlightOff(QPieSlice* slice)
     Q_ASSERT(slice);
     QColor c = slice->brush().color().darker(150);
     slice->setBrush(c);
-    slice->setLabelVisible(false);
 }
 
 void QPieSeries::updateDerivativeData()
@@ -480,7 +491,10 @@ void QPieSeries::updateDerivativeData()
         m_total += s->value();
 
     // we must have some values
-    Q_ASSERT(m_total > 0); // TODO: is this the correct way to handle this?
+    if (m_total == 0) {
+        qDebug() << "QPieSeries::updateDerivativeData() total == 0";
+        Q_ASSERT(m_total > 0); // TODO: is this the correct way to handle this?
+    }
 
     // update slice attributes
     qreal sliceAngle = m_pieStartAngle;
diff --git a/src/piechart/qpieseries.h b/src/piechart/qpieseries.h
index b1fbbc3..96bd797 100644
--- a/src/piechart/qpieseries.h
+++ b/src/piechart/qpieseries.h
@@ -62,6 +62,7 @@ public:
     void add(QList<QPieSlice*> slices);
     void add(QPieSlice* slice);
     QPieSlice* add(qreal value, QString name);
+    QPieSeries& operator << (QPieSlice* slice);
     void remove(QPieSlice* slice);
     void clear();
 
@@ -78,6 +79,8 @@ public:
     void setClickExplodes(bool enable = true);
     void setHoverHighlighting(bool enable = true);
 
+    qreal total() const;
+
     // TODO: find slices?
     // QList<QPieSlice*> findByValue(qreal value);
     // ...