for the synthesis of 0-substituted cyanohydrins from aldehydes and ketones, in the absence of solvent, employing minimum amounts of the corresponding cyanides has been optimised. Aldehydes react more rapidly than ketones using triethylamine as catalyst offering in both cases almost quantitative yields of the corresponding O-trimethylsilyl, O-methoxycarbonyl, O-benzoyl and O-acetyl cyanohydrins.