A thermogravimetric analyzer (TGA) has been interfaced with a microprocessor to study solid/gas reaction kinetics. The TGA measures the change in weight of the solid as the reaction proceeds, thus serving as a microreactor. The TGA is controlled by the microprocessor, and the operating conditions are continuously displayed on the CRT. The system can send data obtained during the course of an experiment to tape storage or to a mainframe computer for further analysis. Software was developed to allow the microprocessor to communicate with two mainframe computers over ordinary telephone lines. This paper discusses the hardware and software which is used for data acquisition and control.