The spontaneous motion of small drops suspended in an immiscible viscous fluid, when an exothermal reaction occurs on their interfaces, has been studied. The heat of reaction results in an elevation of temperature on the drops' interfaces and in the external fluid. The concentration and temperature in the gap region become different from those in the outer regions. The inhomogeneous distribution of concentration and temperature induces surface tension variations, Marangoni type flow and migration of the fluid particles relative to each other. Cases studied concern two drops interaction due to thermocapillary forces induced by temperature field, the addition of a gravity field and the mutual effect of thermocapillary forces induced simultaneously by temperature and concentration. Results are presented for a variety of the governing parameters of the system. Stationary flow patterns with immobile drops configurations are predicted, which appear to be unstable for small perturbations. (C) 2007 American Institute of Chemical Engineers.