A Bangladesh laterite (pH 4·2), in which autotrophic nitrifiers could not be detected, was incubated at temperatures of 30°, 40°, 50° and 60°C at an aerobic moisture content of 50 per cent saturation. Ammonium-N accumulation, which accounted for the major part of the mineralized nitrogen, increased with temperature and time of incubation up to 8 weeks. Nitrate- accumulation was highest at 40° after 4 weeks and at 30°C after 8 weeks. Nitrate accumulation after 8 weeks at 50° and 60°C was 57 and 67 per cent respectively of that at 30°C. At 40°C nitrate produced during the first 4 weeks had virtually disappeared by 8 weeks. Mechanisms of nitrate formation are discussed.