Several new amide derivatives of L-3-carboxymethyIthioalanine were prepared as possible antiviral agents by the alkylation of cysteine. None of these was found to be effective, however. Unrelated to this group, but nonetheless sulfides of cysteine, are L-3-(2-hydroxyethylthio)-alanine and L-3-benzhydrylthioalanine, which were also prepared and tested. The former showed slight activities against a poliomyelitis