Dormison is a drug of a new type that, when used as a hypnotic, is highly efficient and relatively nontoxic and noncumulative. It is the hypnotic of choice in elderly, senile, and arteriosclerotic patients and it has definite advantages over other hypnotics in other types of patients.The hypnotic effect is highly specific, and Dormison is of little value as a sedative since toxic or near-toxic doses are required to produce an adequate sedative effect in disturbed patients. We have observed cumulative effects only when large doses were given as a sedative.The danger of addiction may be less than with other hypnotic-sedative drugs, as Dormison is ultra-short-acting and tends to lack their stupefying and euphorigenic action. Nevertheless, Dormison should not be given as a sedative to patients who have previously been addicted to other drugs, and it should be used as a hypnotic in these cases only under hospital conditions. In view of previous reports, and our findings on cumulation and addiction, barbiturates should not be given to patients receiving Dormison until such time as extensive data are available on the potentiating effect of Dormison on barbiturates in man.