Abstract A series of S-acyl derivatives of β-mercaptoethylamine (MEA) has been prepared in an attempt to provide compounds having protective effects in animal cells against ionizing radiation and which are less toxic than MEA itself. In general, toxicity to animals was reduced and good protective ability against X-radiation was retained in some of the esters. The dithiocarbamic acid of MEA was also prepared, but attempts to acylate this compound ...