The influence of 7.2°, 22°, and 37°C temperature levels on the extent and rates of rice straw decomposition and loss of soil organic matter was investigated in two soils at 60 percent WHC using tracer techniques. About a third of straw-C was lost at 7.2°C within a 4-month incubation period. At all temperature levels, the percentage of straw-C loss after 6 days followed the path of power functions. Differential equations were deduced to describe the instantaneous rate parameter,vi, which decreased with time in asymptotic fashion. Temperature dependence ofviis consistent over the range 7° to 22°C but less so over the range 22° to 37°C. Soil-C loss increased with increasing temperature regardless of straw incorporation. Addition of straw always promoted native soil carbon loss at all temperature levels.Mineralization of straw nitrogen at 7.2° and 22°C was about the same but at 37°C mineralized nitrogen appeared to be lost, possibly as gaseous nitrogen. Soil inorganic nitrogen content increased with increasing temperature, as did the native soil carbon loss.