Even when using KDE as your desktop, there are still gnome/gtk applications that I want to run. I tend to customise my KDE theme quite a bit, and the side effect of this is that the GTK applications stand out like sore thumbs.

The way to ensure your GTK apps look the same (or as close as possible) to your KDE themed apps, is to install the gtk-qt-engine.

To install it on Mandriva, as root, type

urpmi gtk-qt-engine

Others will need to find their own packages, and should check out the project's website.

Once the engine is installed, you can go to the KDE Control Centre and adjust your settings there.