The reactions of trimethyltin hydride and dimethyltin dihydride with (CH3)3SiCF=CF2 and (CH3)2Si(CF=CF2)2 respectively have been investigated. Under thermal conditions, reaction led to organotin fluorides and fluorovinyl-silanes. However, under ultraviolet irradiation at 25°, addition products were isolated of which (CH3)3SiCFHCF2Sn(CH3)3 and (CH3)3SiCF[Sn(CH3)3]CF2H were fully characterized. Evidence is presented which shows that these addition products are formed by a free radical process and that their decomposition to organotin fluorides and fluorovinyl-silanes proceeds via a β-fluorine elimination. Spectroscopic data are presented for a number of new organo-silanes.