Novel benzyloxycarbonyl derivatives of 2-aminoethanethiol (H2NCH2CH2SH, 1) have been prepared and characterised, and their thermal behaviour studied by thermogravimetry, differential thermogravimetry and differential scanning calorimetry. Thermal data indicate that compounds of the type C6H5CH2OC=OS(CH2)(2)NH(3)(+)X(-)(where X is Cl-, Br- or I-) melt and decarboxylate to give, predominantly, the corresponding benzyl derivative C6H5CH2S(CH2)(2)NH(3)(+)X(-). Related compounds of the type C6H5CH2OC=OS(C-2)(2)NHO=COCH2C6H5, [C6H5CH2OC=ONH(CH2)(2)S](2) and C6H5C-OS(CH2)(2)NHO=COCH2C6H5 showed no tendency to decarboxylate.