The potentiostatic pulse technique proved to be the most powerful electrochemical technique for in situ studies of the early stages of Bi2S3 electrodeposition on bismuth. The current-time response recorded at the overpotentials in the vicinity of E-r (Bi2S3/Bi) in dependence of hydrogen sulfide ion concentrations, was described by a theoretical expression for three-dimensional progressive nucleation and growth under diffusion control. Through the application of relations which hold true for such a nucleation model, the following parameters were determined: (i) the anodic nucleation potential (E-AN); (ii) the rate of nucleation (AN(infinity)); (iii) the diffusion coefficient (D); and (iv) the density of the growing sites (N-s).