R e c e i v e d 1 8 / 1 0 / 7 8 -A c c e p t e d 6/11/78 ABSTUCT The force f i e l d study o f ble3SbX2 ( X = F, C 1 , B r , I ) molecules of D3h symmetry has been c a r r i e d o u t by Redington's approach t r e a t i n g t h e methyl group as point masses. The force constants, mean amplitudes of v i b r a t i o n , bond charge and p a t h l e n g t h parameters and r o t a t i o n d i s t o r t i o n constants l;&-re a l s o been calculated and compared with t h e l i t e r a t u r e values whichever is available.