The HTK-1200 is a new High Temperature Oven Chamber which is designed for x-ray powder diffraction studies from room temperature up to 1200 degrees C under air or inert gas. The chamber is designed to be fit on most commercially available goniometers, both vertical and horizontal ones (Fig.1). The main advantage of an oven chamber is the high temperature uniformity inside the chamber, which ensures a very low temperature gradient within the sample (Fig. 2). A special design of detachable low cost ceramic sample holders provides easy handling, simplifies sample preparation and allows different sizes and materials (Fig. 6). Sample displacement can be compensated precisely using a motor driven alignment stage (Fig. 5).