The reaction of (Z)-1-halo-1-alkenyldialkylborane (1) with tributyltin hydride (n-Bu3SnH) at 0° C or room temperature results in reductive removal of the halogen atom to afford (E)-or (Z)- 1-alkenyldialkylborane whose stereochemistry depends on the dialkylboryl group and the alkenyl group of 1.