Chemistry Department, Agra College, Agra-282 002 Manuscript received 28 May 1986, revised 4 February 1988, accepted 5 February 1988 Polarographic behaviour of DDD and BHC in aqueous solutions containing 4% dimethylformamide (DMF) and 50% ethanol has been studied at 25 ±0.1° in Britton —Robinson (BR) buffer of pH 7.0 in presence of varying concentrations (0.05 — 0.50 M) of different supporting electrolytes, viz. tatramethylammonium bromide (TMAB), KCI, KBr, KCNS, KNO3, NaNO3, and NH4NOs. Each depolariser is reduced in two steps which are diffusion-controlled and irreversible. The kinetic parameters (αna and \(k^o_{f.h}\)) of the electrode reactions have been calculated by Koatecky's method. A decrease in the values of kinetic parameters shows that the irreversible electrode reactions of DDD and BHC tend to become increasingly more irreversible with the increasing concentra­tion of different supporting electrolytes. The results have been explained in terms of double layer structure.