Triorganogallium and -indium reagents reacted with alpha,beta unsaturated nitrile and carbonyl compounds to give 1.4-addition products regioselectively. The reaction of allylgallium and allylindium sesquihalides with alpha,beta-unsaturatedcarbonyl compounds proceeded in a 1,2-addition mode, whereas a 1,4-addition took place with alpha,beta-unsaturated nitriles. (C) 1999 Elsevier Science Ltd. All rights reserved.