New data are presented on the antimony pentafluoride catalyzed reaction of hydrofluorocarbons such as CH 3 F, CH 2 F 2 , CH 3 CHF 2 and R f CH 2 CH 2 F with fluoroolefins. The condensation of CH 2 F 2 and fluoroolefins CF 2 CFX (X=F, CF 3 ) proceeds under mild conditions producing the corresponding propanes FCH 2 CFXCF 3 in moderate to high yield. Under similar conditions methyl fluoride reacts with tetrafluoroethylene giving CH 3 CF 2 CF 3 . However, a complex mixture of products forms in the analogous reaction with hexafluoropropene. The structures of the products of the reactions of CH 3 CHF 2 and tetrafluoroethylene and F-butylethylene were determined.