In this work, a simple comprehensive mathematical model, to understand the main mechanisms occurring in the semicontinuous heterophase inverse polymerization of acrylamide, is reported. A Mayo-Lewis extended model, including nucleation and coagulation, is assessed with experimental conversion, particle density and inferred average number of radicals versus time-data at 60 degrees C, at three monomer addition rates. It was found that: (1) the average number of radicals is much smaller than 0.5 contrary to most of inverse emulsion and microemulsion polymerization reports, this number increased steadily along the experiments, (2) coagulation does exist in this process, and (3) the exit rate coefficient was found to present a high value, agreeing with other authors that claim a large exit rate. Conversion, the bell-shaped number of particles' evolution and number average radicals' concentration, versus time data, are well described by the proposed model. POLYM. ENG. SCI., 58:2219-2226, 2018. (c) 2018 Society of Plastics Engineers