Dimethazan is a caffeine derivative. Dimethazan differs from caffeine by the replacement of the third methyl group. Dimethazan possesses antidepressant and diuretic properties. Dimethazan, administered intravenously to geriatric patients, produced respiratory and cerebral stimulation in the majority of cases. The clinical utilization of the respiratory stimulatory effect was confirmed in a patient markedly depressed with chlorpromazine. Oral administration to patients hospitalized for treatment of mental and physical depression indicated a dual effect: central nervous system stimulation and sedation. It is safe and well tolerated with none of the shortcomings of other caffeine preparations.