Effects of experimental exposure to toluene (3.2 mmol/m3, ie, 300 mg/m3) for 4.5 h and ethanol ingestion (15 mmol/kg) on the results of four performance tests, symptoms, mood, and physiological indices of wakefulness were studied in 12 male volunteers. Toluene exposure produced symptoms like headache and local irritation, as well as a weak depression of heart rate during rest, but did not reduce performance capability. Ethanol ingestion impaired performance on two of the tests and also increased heart rate. Mood was likewise altered by ethanol, but no increase in subjective symptoms due to ethanol ingestion could be demonstrated. Physiological indices of wakefulness were not affected by toluene exposure or by ethanol intake. No interaction effects were found.