Neutropenic patients receiving amphotericin B, frequently in combination with aminoglycosides and vancomycin, were prospectively monitored for the development of nephrotoxicity. Based on previous studies, the authors recommended that these patients receive greater than or equal to 90 meq of sodium/day on each day of amphotericin B administration. Patients who received this amount of sodium on every day of amphotericin B therapy were classified as adequate sodium. The adequate sodium group was further subdivided on the basis of whether or not the adequate sodium was in the form of sodium ticarcillin. Patients not receiving this amount of sodium on every day of amphotericin B therapy were classified as inadequate sodium; overall, these patients received greater than or equal to 90 meq of sodium/day on 74% of days on which they received amphotericin B. The inadequate sodium and adequate sodium groups did not differ significantly with respect to age, gender, diagnoses, or baseline creatinine. The incidence of nephrotoxicity (creatinine greater than or equal to 2.0 mg/dl) was significantly higher, 4 of 14 (29%), in the inadequate sodium group, as compared to the adequate sodium, adequate ticarcillin group, 1 of 35 (3%), or the adequate sodium only group, 1 of 24 (4%), p = .008. To adjust for total amphotericin dose, the risk of nephrotoxicity as a function of time on study was evaluated by the life table method; the risk of nephrotoxicity was significantly greater in the inadequate sodium group, p = .019.(ABSTRACT TRUNCATED AT 250 WORDS)