The functional expression of papillary necrosis was investigated with a model of drug-induced papillary necrosis. Bromoethylamine hydrobromide (BEA) administration to rats uniformly resulted in the development of papillary necrosis. All studies were performed 24 hours after BEA administration with the exception of the electrolyte balance studies, which were performed during the 72 hours after the induction of papillary necrosis. GFR was not different between BEA-treated and sham rats. BEA-treated rats had a significantly lower maximal urine osmolality and free water reabsorption than did sham rats. Renal tissue concentrations of sodium, potassium, and water were not different between BEA-treated and sham rats. During water diuresis, free water clearance was not significantly different between the two groups. During sodium bicarbonate administration, maximal bicarbonate reabsorption and urine-blood Pco2 gradient (at comparable urine bicarbonate concentrations) were not significantly different between the two groups. During sodium sulfate infusion, there was no difference in minimum urine pH, ammonium excretion, and net acid excretion between chronically acidotic BEA-injected and sham rats. In rats on "zero" sodium intake, BEA administration resulted in a significant increase in urine flow and sodium excretion, whereas sham rats remained in sodium balance. In rats with restriction of both sodium and chloride, BEA administration resulted in a significant wastage of sodium, chloride, and calcium. There was no difference in potassium excretion between BEA-treated and sham rats during hydropenia, bicarbonate administration, sodium sulfate infusion, or ingestion of a normal potassium diet. When potassium intake was restricted to "zero," BEA-treated rats developed potassium wastage; when potassium intake was increased to 21 mEq/day, BEA-treated rats had a significantly lower potassium excretion than did sham rats. These findings may result from alterations in collecting duct transport, but damage to deep medullary structures may also contribute.