A review is given of the synthesis, physical properties, and decomposition kinetics of organic peroxycarbamates. The activity of these compounds in initiating free‐radical vinyl polymerization is discussed. The decomposition of hexamethylene N,N′‐bis‐(α‐cumyl peroxycarbamate) has been measured in different solvents between 65 and 95°C and found to be a first‐order reaction governed by the specific rate constant kd = 2.21 × 1016 exp {−34 100/RT}. The initiator exhibits normal free‐radical polymerization kinetics and in polymerization of styrene at 80°C shows an initiating efficiency of 0.53. Cobalt naphthenate can act as both accelerator and retarder of styrene polymerization, depending upon its concentration and the temperature of the polymerization.