Chemical renal medullectomy with 2‐bromo‐ethylamine hydrobromide (BEA) has been used to study the importance of the renal medulla in blood pressure regulation. However, conclusive evidence as to whether BEA treatment affects the glomerular barrier is lacking. In the present study, the effects of BEA upon glomerular permselectivity for albumin were studied using isolated kidneys (IPK) perfused at a low temperature (8 °C) to inhibit tubular reabsorption of proteins. Sixteen WKY rats (WB) received an i.v. injection of BEA (150 mg kg‐1) while 10 rats served as controls (WC). Volume balance, urinary osmolality and creatinine clearance (GFR) were measured in metabolic cages. Acute paired experiments (n=9) were performed 5–7 weeks after BEA. The rats were anaesthetized and the totalin vivoalbumin excretion was recorded. The kidneys were then isolated and perfused for measurements of inulin clearance (GFR) and fractional albumin clearance without tubular reabsorption of protein. The nine BEA treated rats showed polyuria and hypoosmotic urine.In vivoGFR was lower in the BEA treated groups when measured with creatinine clearance (459±22 vs. 213±41 μL min‐1100 g‐1body wt,P<0.001), while GFR was not significantly changed in the IPK (WC=135±27, WB=92±14 μL min‐1100 g‐1body wt, n.s.) when perfused at identical pressures. The fractional albumin clearance was increased three times in the BEA group (WB=9.6±3.4J,P<0.05). Moreover, albumin excretionin vivowas similar in the two groups despite low GFR in the BEA group. We conclude that BEA treatment affects glomerular perm