To the Editor.— In my case report of Marihuana Psychosis ( 212: 1527, 1970), I emphasized the following medically important features of psychiatric acute adverse reactions to marihuana: (1) the relative mildness of their course, (2) their transient nature, and (3) infrequency of their occurrence. Perna ( 214: 760, 1970) claims that my views do not represent a statement of fact and are dangerously misleading. A review of recent reports on the subject clarifies some points. Comparison of the effects of marihuana and alcoholic intoxication is valid as both produce similar effects of relaxation, tension-reduction, and sense of well being. 1 2. The frequency of psychiatric acute adverse reactions to marihuana in non-psychiatric populations was recorded by Pillard. 2 An informal survey of the Boston University Student Health Service, which cares for a student population of 20,000, revealed that only 5-7 marihuanaassociated anxiety reactions are being seen yearly. He also refers