Pathways were investigated for the Cr transfer from the dialysate into the bloodstream as observed during continuous ambulatory peritoneal dialysis (CAPD). As the presence of Cr(VI) in the dialysate can be ruled out, due to reduction by lactate, a common compound of dialysate, all experiments were aimed at studying the behaviour of Cr(III). The ability of Cr(III) to penetrate across membranes at physiological pH was investigated. The characteristics during ‘in vitro’ dialysis were compared to the behaviour during acute ‘in vivo’ peritoneal dialysis in anesthetized rabbits. It appeared that lactate plays an important role in the mobility and the subsequent peritoneal Cr transfer.