Hi. I investigated a little bit more (Octave 3.0.0+ and Gnuplot 4.2.2). The following contourf(peaks) axis([1 49 1 49]) does not show the tick markers. But the following contourf(peaks) axis([2 48 2 48]) yes, at least where the fill color is white. So, it seems that not-white regions overwrite the tick markers. Best regards, Marco