The electrochemical study of some 2-mercapto-5-R-ammino-1,3,4-thiadiazole derivatives was made by cyclic and linear sweep voltammetry using a carbon paste electrode (CPE, graphite/solid paraffin ratio 2:1) as working electrode and an Ag/AgCl reference electrode. The current–potential curves were recorded in anodic polarisation in −0.1 and +1.3 V range using aqueous solutions and different buffers (between pH 1.2 and 10.0), with 20 or 50 mV s −1 sweep rate. The oxidation peak appears between +0.65 and +0.70 V due to disulphides formation. The 5-phenyl derivative has two oxidation peaks, the first at +0.45±0.03 V and the second at +0.65±0.03 V. The oxidation potentials are pH dependent, decreasing from 0.9±0.1V at pH 1.2 to 0.6±0.1 V at a pH between 8.0 and 10.0. In some potential ranges depending on pK a of molecules the oxidation potential and oxidation current are pH independent. Simple, precise and accurate voltammetric methods for the determination of these compounds were developed and validated in 2.5×10 −6 –7.5×10 −4 mol l −1 concentration ranges. The detection limits were 2.3 μmol l −1 for 5-ammino-, 12.3 μmol l −1 for 5-acetylammino-, 11.6 μmol l −1 for 5-allylammino-, and 1.2 μmol l −1 for 5-phenylammino-2-mercapto-1,3,4 thiadiazole derivatives.