An efficient method for the conjugate addition of unactivated alkyl iodides to α, β-unsaturated carbonyl compounds using indium/copper in water is described. The reactions proceed more efficiently in water than in organic solvents. In, CuI, and InCl3 are all essential for efficient reaction. Formation of a symmetrical vic-diarylalkane is observed when an aryl- substituted alkene is used as substrate.