An audit of 2,641 toxicology requests from the Georgetown University Hospital Emergency Department from 1981 through 1984 was conducted to assess the contribution of toxicology laboratory results to the clinical evaluation of the intoxicated patient. Positive findings were obtained in 80% of the patients tested. Ethanol was the most common intoxicant, accounting for 48% of all positive results and an average serum concentration of 250 mg/dl. Multiple drug use was documented in 28% of the patients with positive results; some ingested as many as six substances. Women were more likely than men to be polydrug users. A comparison of laboratory findings with diagnosis based on history and examination for 76 patients revealed that the laboratory provided additional information on the nature of the intoxication two-thirds of the time. Our conclusion is that the toxicology laboratory offering a broadly based screening service when properly utilized by the emergency department staff can aid in establishing an accurate diagnosis and provide a guide to therapy in the intoxicated patient.