Sunflower, soybean, corn and arachis oils were microwave-heated (1000 W) for 40 mm to follow the changes in peroxide, anisidine, acid and I nos., in totox index as well as in their d. and viscosity. An increase in the measured values during the expt. course was obsd. The kinetics of the anisidine no. change was described by polynomial equation for the studied oils.