BACKGROUND Nephrotoxicity is an important side effect of amphothericin B deoxycholate (ampho B) and cyclosporine A (CsA). The combined administration of these drugs is frequent in patients with haematological diseases undergoing allogeneic stem cell transplantation. OBJECTIVE To assess the additional renal toxicity of ampho B given as a continuous infusion in addition to CsA. METHODS In a retrospective study renal function was investigated in patients receiving CsA alone or in combination with ampho B (24-hour infusion) after allogeneic stem cell transplantation between January 1998 and April 2001. RESULTS Of a total of 84 patients, 22 were treated with ampho B. There was a statistically significant decline in renal function in comparison to the 62 patients receiving CsA alone. However, renal insufficiency in all patients remained in a clinically acceptable range and was reversible. The residual renal dysfunction at the end of the hospitalisation was mainly due to continuing therapy with CsA. CONCLUSIONS Amphotericin B deoxycholate in addition to CsA leads to a statistically significant but clinically tolerable worsening of renal function. Using a 24-hour infusion and strict salt repletion, amphotericin B can be administered safely as deoxycholate in bone marrow transplant patients in conjunction with CsA for proven or suspected fungal infections.