A patient with acute ethylene glycol poisoning was treated with ethanol administration and hemodialysis, and his renal function remained consistently normal. Serial measurements of serum and urine levels of urea, creatinine, ethylene glycol, and ethanol were performed to compare the relative contributions of the hemodialyzer and the patient's kidneys in clearing ethylene glycol from the blood. Simultaneous measurements of the serum-osmolal gap (corrected for ethanol) and anion gap were correlated with these data. Mean renal clearance of ethylene glycol was 27.5 +/- 4.1 ml/min, with a fractional ethylene glycol excretion of 19.8 +/- 1.5%. This was lower than the mean urea clearance of 89.4 +/- 11.0 ml/min and fractional urea excretion of 66.0 +/- 7.8%. Hemodialyzer clearance of ethylene glycol was 156 ml/min. There was a nearly exact correlation between the serum ethylene glycol level and the corrected osmolal gap (r = 0.998, p less than 0.01). The calculated renal elimination half-life of ethylene glycol was 18 hr. We conclude that with a moderate diuresis, the normal human kidney contributes significantly to the removal of ethylene glycol from the blood. Corrected serum osmolal gap provides a nearly exact approximation of the serum ethylene glycol level and is a useful therapeutic guide.