The chemical nature of the urinary odour produced by man after asparagus ingestion.

1. The pungent urinary odour produced by certain individuals within a few hours of eating asparagus has been shown to be due to a combination of up to six sulphur-containing alkyl compounds identified as methanethiol, dimethyl sulphide, dimethyl disulphide, bis-(methylthio)methane, dimethyl sulphoxide and dimethyl sulphone. 2. The possible roles of S-methylmethionine and asparagusic acid as precursors of these odorous substances are discussed in relation to the known chemistry of the vegetable.