Some derivatives of 1,1'-thiobis(2-chloroethane) (sulphur mustard) have been synthesised for use as reference compounds in a wide range of studies embracing analysis, metabolism, environmental degradation and decontamination. Compounds include products formed by hydrolysis, substitution and elimination reactions and their oxidised sulphoxide and sulphone analogues. A comprehensive series of methylthio, methylsulphinyl and methylsulphonyl derivatives has been synthesised in support of metabolic studies.