Novel benzyloxycarbonyl derivatives of 2-aminoethanethiol (H 2 NCH 2 CH 2 SH, 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 C 6 H 5 CH 2 OC=OS(CH 2 ) 2 NH + 3 X - (where X is Cl - , Br - or I - ) melt and decarboxylate to give, predominantly, the corresponding benzyl derivative C 6 H 5 CH 2 S(CH 2 ) 2 NH + 3 X - . Related compounds of the type C 6 H 5 CH 2 OC=OS(C 2 ) 2 NHO=COCH 2 C 6 H 5 , [C 6 H 5 CH 2 OC=ONH(CH 2 ) 2 S] 2 and C 6 H 5 C=OS(CH 2 ) 2 NHO=COCH 2 C 6 H 5 showed no tendency to decarboxylate.