Trichloromethyl- and tribromomethyl-tributyltin give adducts with aldehydes. On acidolysis the corresponding trichloromethyl- and tribromomethylcarbinols are obtained in good yields. The stereochemistry of the addition reaction with hydratropic aldehyde was investigated and the substituent effects were determined by means of competitive experiments with substituted benzaldehydes. The inefficiency of