Volume, specific gravity, creatinine, lactate dehydrogenase (LDH), leucine aminopeptidase (LAP), betagalactosidase (GAL), leucocytes, erythrocytes, nitrite, protein (albumin), glucose, ketone, urobilinogen, bilirubin and pH were estimated in urine of rats after single (by gavage) or repeated (via drinking water) oral administration of diethylene glycol (DEG). Following single or repetitive doses (daily over 90 days) of 0.2 g DEG kg-I body weight, no change in renal function was observed (no effect level). In urine of rats treated once with 0.7 g DEG kg-' body weight, LDH activity was significantly enhanced one day after treatment. A single dose of 2.0 g DEG kg-' body weight resulted in an additional rise in urinary GAL activity two days after treatment, a significant rise of urinary volume and a decrease in creatinine concentration and pH on the first day. One day following a single dose of 8.0 g DEG kg-' body weight, in addition to the changes mentioned before, LAP activity was significantly elevated and the specific gravity decreased. However, in all experiments the wet weight of the kidneys remained normal as compared to controls. The results thus show dose-dependent changes in several renal parameters, indicating a slight-to-moderate and reversible renal impairment.