Deep coma resulting from barbiturate overdose was studied in 50 patients. The length of coma correlated with depth of coma and serum barbiturate level except in those patients with drug addiction and hepatic or renal disease. The complications of pneumonia, bleeding of the gastrointestinal tract, urinary tract infections, and thrombophlebitis were common; however, all patients survived. Treatment was instituted on a rotation basis with supportive care alone, mannitol diuresis, or peritoneal dialysis. Using length of coma, the slope of disappearance of serum barbiturate value, and clearance data as indicators of the effectiveness of treatment, we found that the three treatment forms did not differ. Supportive care alone was associated with less local and systemic morbidity and appears to be the best method of reducing morbidity and mortality in patients with barbiturate overdose.