Adsorption studies of Sb (III) as the antimonyl (125Sb) tartrate complex using acidified, non-proliferative suspensions of Mycobacterium smegmatis show that the uptake of Sb by the biomass increases with the external concentration of antimony ([Sb]) and decreases, at given concentration, with increasing pH. Measurements of Sb uptake in the cells under growth conditions in liquid culture indicate that the cellular concentration factor of antimony is of the order of 10 when the concentration of antimony in the medium is 10 microM, i.e., close to the minimum inhibitory concentration.