The fate of 3H- and 14C-labelled A-4166 was examined in rat pancreatic islets. The net uptake of the meglitinide analogue by islets incubated for 60 min in the presence of 0.1 mM A-4166 and then submitted to repeated washes was close to 0.1 pmol/islet. It was significantly increased when the concentration of D-glucose in the incubation medium was raised from 2.8 to 16.7 mM. No sizeable internalization of tritiated A-4166 into insulin-producing cells could be detected by autoradiography. These findings suggest that the interaction of A-4166 with the beta-cell may be restricted to its insertion on the plasma membrane and binding to sulphonylurea receptors.