Abstract: The binding of arsenic (As) on bovine serum albumin (BSA) was studied by equilibrium dialysis (ED) method using warfarin sodium (as site-I specific probe) and diazepam (as site-II specific probe) to determine the binding sites of arsenic to BSA. The data obtained showed that the free concentration of warfarin sodium increased very slowly by the addition of arsenic, while the free concentration of diazepam increased rapidly by the addition of arsenic. The free concentration of warfarin was 10.5% in absence of arsenic whereas this release was up to 20% when arsenic was added to BSA with an increasing concentration from 0.5x10-5 to 10x10-5M. The free concentration of diazepam was 11% in absence of arsenic whereas this release was up to 50% when arsenic was added to BSA with an increasing concentration from 0.5x10-5 to 10x10-5M. This site-specific probe displacement data implied that site-I (warfarin site) is low affinity site while site-II (diazepam site) is high affinity site of arsenic to the BSA.