Emulsion copolymerization of tetrafluoroethylene (TFE) and propylene (P) initiated by trilon-rongalite catalytic system containing tert-C4H9OH, initial monomer mixture, emulsifier (C7F15COONH4) concentration, and monomer mixture/water ratio on the polymerization rate (R) and molecular weight (MBAR(n)) was investigated. Both R and MBAR(n) increased considerably with TFE content in monomer mixture up to 75 mol %. Alternating rubberlike copolymers in a wide range of initial monomer mixture (from 55-85 mol %) were obtained. The reactivity ratio was found to be r(TFE) = 0.005 +/- 0.04 and r(p) = 0.17 +/- 0.07. Above the critical micelle concentration, the effects of the initiating system Is and emulsifier Cs on R and MBAR(n) were found to obey the following relations : R is-proportional-to [Is]0.54 x [Cs]0.42 and MBAR(n) is-proportional-to [Is]-0.1 x [Cs]0.1, according to which emulsion copolymerization proceeds by the I case of Smith-Ewart theory. Polymerization mechanism of the reaction studied was suggested. The copolymerization is mainly terminated by degradative chain transfer of the propagating radicals to propylene.