The kinetics of the soln. polymn. of Me methacrylate is characterized by a strong increase of viscosity of ?6 orders of magnitude and autoacceleration of the reaction rate due to the gel effect. This can lead to thermal and kinetic reactor instabilities. The kinetics is detd. sep. using DSC and described with a modified published model. The model predictions are verified in pilot plant expts. at 130-170 Deg. [on SciFinder (R)]