diff --git a/src/MainWindow.cpp b/src/MainWindow.cpp
index aad6cb6a9..2fb9c4e73 100644
--- a/src/MainWindow.cpp
+++ b/src/MainWindow.cpp
@@ -299,11 +299,16 @@ MainWindow::MainWindow(const QDir &home) :
                                                      binWidthLineEdit));
     binWidthLayout->addWidget(binWidthSlider);
 
+    lnYHistCheckBox = new QCheckBox;
+    lnYHistCheckBox->setText("Log y");
+    binWidthLayout->addWidget(lnYHistCheckBox);
+
     withZerosCheckBox = new QCheckBox;
     withZerosCheckBox->setText("With zeros");
     binWidthLayout->addWidget(withZerosCheckBox);
 
     powerHist = new PowerHist();
+    lnYHistCheckBox->setChecked(powerHist->islnY());
     withZerosCheckBox->setChecked(powerHist->withZeros());
     binWidthSlider->setValue(powerHist->binWidth());
     binWidthLineEdit->setText(QString("%1").arg(powerHist->binWidth()));
@@ -378,6 +383,8 @@ MainWindow::MainWindow(const QDir &home) :
             this, SLOT(setBinWidthFromSlider()));
     connect(binWidthLineEdit, SIGNAL(editingFinished()),
             this, SLOT(setBinWidthFromLineEdit()));
+    connect(lnYHistCheckBox, SIGNAL(stateChanged(int)),
+            this, SLOT(setlnYHistFromCheckBox()));
     connect(withZerosCheckBox, SIGNAL(stateChanged(int)),
             this, SLOT(setWithZerosFromCheckBox()));
     connect(qaCPValue, SIGNAL(editingFinished()),
@@ -1100,6 +1107,13 @@ MainWindow::setBinWidthFromSlider()
     }
 }
 
+void
+MainWindow::setlnYHistFromCheckBox()
+{
+    if (powerHist->islnY() != lnYHistCheckBox->isChecked())
+	powerHist->setlnY(! powerHist->islnY());
+}
+
 void
 MainWindow::setWithZerosFromCheckBox()
 {
diff --git a/src/MainWindow.h b/src/MainWindow.h
index e33f08575..c171a0fac 100644
--- a/src/MainWindow.h
+++ b/src/MainWindow.h
@@ -65,6 +65,7 @@ class MainWindow : public QMainWindow
         void setSmoothingFromLineEdit();
         void setBinWidthFromSlider();
         void setBinWidthFromLineEdit();
+	void setlnYHistFromCheckBox();
         void setWithZerosFromCheckBox();
         void setQaCPFromLineEdit();
         void setQaCADFromLineEdit();
@@ -104,6 +105,7 @@ class MainWindow : public QMainWindow
         QLineEdit *smoothLineEdit;
         QSlider *binWidthSlider;
         QLineEdit *binWidthLineEdit;
+        QCheckBox *lnYHistCheckBox;
         QCheckBox *withZerosCheckBox;
         QTreeWidgetItem *allRides;
         PowerHist *powerHist;
diff --git a/src/PowerHist.cpp b/src/PowerHist.cpp
index e9613e945..66c68c005 100644
--- a/src/PowerHist.cpp
+++ b/src/PowerHist.cpp
@@ -23,11 +23,12 @@
 #include <assert.h>
 #include <qwt_plot_curve.h>
 #include <qwt_plot_grid.h>
+#include <qwt_scale_engine.h>
 #include <qwt_legend.h>
 #include <qwt_data.h>
 
 PowerHist::PowerHist() :
-    array(NULL), binw(20), withz(true)
+    array(NULL), binw(20), withz(true), lny(false)
 {
     setCanvasBackground(Qt::white);
 
@@ -48,6 +49,11 @@ PowerHist::PowerHist() :
     grid->attach(this);
 }
 
+PowerHist::~PowerHist() {
+    delete curve;
+    delete grid;
+}
+
 void
 PowerHist::recalc()
 {
@@ -63,11 +69,11 @@ PowerHist::recalc()
         if (low==0 && !withz)
             low++;
         smoothWatts[i] = low;
-        smoothTime[i]  = 0.0;
+        smoothTime[i]  = 1e-9;   // non-zero for log axis
         while (low < high)
             smoothTime[i] += array[low++] / 60.0;
     }
-    smoothTime[i] = 0.0;
+    smoothTime[i] = 1e-9;
     smoothWatts[i] = i * binw;
     curve->setData(smoothWatts.data(), smoothTime.data(), count+1);
     setAxisScale(xBottom, 0.0, smoothWatts[count]);
@@ -78,7 +84,7 @@ PowerHist::recalc()
 void
 PowerHist::setYMax() 
 {
-    setAxisScale(yLeft, 0.0, curve->maxYValue() * 1.1);
+    setAxisScale(yLeft, (lny ? 0.1 : 0.0), curve->maxYValue() * 1.1);
 }
 
 void
@@ -123,3 +129,27 @@ PowerHist::setWithZeros(bool value)
     recalc();
 }
 
+void
+PowerHist::setlnY(bool value)
+{
+    // note: setAxisScaleEngine deletes the old ScaleEngine, so specifying
+    // "new" in the argument list is not a leak
+
+    if (lny = value) {
+	setAxisScaleEngine(
+			   yLeft,
+			   new QwtLog10ScaleEngine
+			   );
+	curve->setBaseline(1e-6);
+    }
+    else {
+	setAxisScaleEngine(
+			   yLeft,
+			   new QwtLinearScaleEngine
+			   );
+	curve->setBaseline(0);
+    }
+    setYMax();
+    replot();
+}
+
diff --git a/src/PowerHist.h b/src/PowerHist.h
index c93741e22..a00d9db2c 100644
--- a/src/PowerHist.h
+++ b/src/PowerHist.h
@@ -34,15 +34,18 @@ class PowerHist : public QwtPlot
         QwtPlotCurve *curve;
 
         PowerHist();
+        ~PowerHist();
 
         int binWidth() const { return binw; }
 
-        bool withZeros() const { return withz; }
+        inline bool withZeros() const { return withz; }
+        inline bool islnY() const { return lny; }
 
         void setData(RideFile *ride);
 
     public slots:
 
+        void setlnY(bool value);
         void setWithZeros(bool value);
 
         void setBinWidth(int value);
@@ -54,7 +57,8 @@ class PowerHist : public QwtPlot
         double *array;
         int arrayLength;
 
-        bool withz;
+        bool withz;   // whether P=0 are omitted from hisogram
+	bool lny;     // whether y-axis is a log scale
 
         int binw;