A high-resolution double-crystal X-ray diffractometer to carry out diffraction experiments in situ at high temperature was projected and constructed at ITN with the incorporation of some basic commercial components, namely the X-ray source and sample goniometer. The software for the remote control, data acquisition and some of the data analysis was developed locally as an integrated package using Labview for Windows, being compliant with windows NT/98/2000. The instrument is particularly suited for in-situ decomposition studies. Although it can perform a large variety of other experiments both in single and polycrystalline samples, namely reciprocal space maps (Omega -2 theta and psi -2 theta), residual strain-texture correlations, powder diffraction, integral Omega scans, etc. All these experiments can be performed from room temperature up to 1400 degreesC.