A combination small and wide angle diffractometer is described. This instrument permits collection of both small angle and normal diffractometer data as a specimen is subjected to mechanical, chemical, or thermal treatment. Curved crystal focusing optics is utilized. The useful range of the apparatus is 0.023 to approximately 60° 2&thgr;. The apparatus has the following features: (1) excellent resolution over the entire usable angular range (the focused primary beam has a half‐breadth of 4×10−4rad); (2) simplicity of design; (3) monochromatization of x rays; (4) ample specimen space, enabling one to heat, deform, or otherwise perturb specimensin situ. The unit utilizes a ground and bent quartz crystal, a Picker diffractometer, and a Hilger microfocus x‐ray tube and generator. The basic unit can be assembled largely from factory‐available apparatus, the exceptions being special mounts for the x‐ray tube and the monochromator. The alignment procedure is briefly outlined and the positions of the necessary adjusting devices are described. A specimen heater, incorporated in this instrument and accurate to ±¼ C° from room temperature to about 150°C, is described. The heater utilizes the passage of hot gases to maintain the temperature. Finally, small and wide angle scattering curves are shown to illustrate the utility of the apparatus.