Silver oxide was found to be an excellent catalyst for allylation reactions of allyltributyltins with aldehydes in aqueous media. Despite the very low solubility of silver oxide in the media, the reactions proceeded smoothly, and the catalyst was recovered and reused. When a-methyl-substituted allyltributyltin was used as the nucleophile, the corresponding a-adducts were obtained exclusively in high yields with good anti-selectivity. A reaction mechanism including transmetalation from tin to silver is proposed.