Hemoperfusion has been increasingly used to treat drug intoxication. Although efficient extraction rates have been reported with hemoperfusion devices, simultaneous measurements of drug adsorption on the columns and endogenous clearance rates have not been made. We studied three patients who ingested 12 to 22 g of ethchlorvynol (Placidyl). In each patient saline diuresis was induced, and Amberlite XAD-4 resin hemoperfusion was done. Resin extraction of ethchlorvynol was calculated hourly, and the recovery of drugs from each column was measured. Renal clearance of ethchlorvynol was simultaneously measured. The resin removed 100% of perfused ethchlorvynol measured by gas chromatography. Ethchlorvynol recovery from the columns agreed well with calculated extraction. Renal clearance was 1 to 6 mL/min, and estimated metabolic clearance was 16% to 31% of resin extraction rate. Complications included anemia, thrombocytopenia, hypocalcemia, and pancreatitis. Resin hemoperfusion substantially supplements endogenous clearance of ethchlorvynol and is a valuable therapy in ethchlorvynol intoxication.