Abstract: A method of on-line monitoring and control of monomer conversion in emulsion polymerization includes continuously balancing, as from an initialization time, the heat QIN, introduced into the reactor, the reaction enthalpy QRE introduced via the monomer feed, and the heat which has been removed from the reactor QOUT, and calculating an amount of heat which has not been removed QAD which would lead to an increase in the internal temperature and the internal pressure of the reactor in the event of a spontaneous adiabatic reaction. A check is carried out as to whether the potential adiabatic temperatures and pressures always lie below prescribed upper limits. If the upper limits are exceeded, the monomer feed to the reactor is throttled back or interrupted.