In recent years great interest has been aroused in the use of the alkaloid reserpine (I) in the treatment of hypertension and various mental disorders. The roots of Razcwoljia serpentina Benth., a member of the family Apocynaceae, from which the alkaloid mas originally isolated by R!ueller, Schlittler, and Bein (1952), have been used for centuries in India as a sedative, and have been the main commercial source. Further export of this material from India has been banned (Editorial 1955) and although the demand has been partially met by other eastern countries such as Burma, Siam, and Java, and by the use of other reserpine-containing species such as R. vomito.i.ia Bfz. (Poisson et al. 1964) and R. heterophylla Roem. et Schult. (Djerassi et al. 1953), an intensive search for new sources is being conducted by the pharmaceutical firms concerned in exploitation. We wish to report the presence of reserpine in the root bark of Alstonia constricts F. Muell. ('bitter bark'), a small tree confined to north-eastern Australia and occurring in the Queensland rain-forests. No attempt at complete isolation of the alkaloids has been made, but reserpine has been isolated in approximately 0.05 per cent. yield and identified by comparison with an authentic specimen and by hydrolysis to reserpic acid and 3,4,5-trimethoxybenzoic acid. The results of assays based on the amount of the latter acid produced on hydrolysis of the crude tertiary bases are shown in Table 1. These values cover all alkaloids which produce a non-volatile acid on hydrolysis, but since substantially pure 3,4,5-trimethoxybenzoic acid was produced in each case, rescinnamine (Klohs, Draper, and Keller 1954) was probably absent. Deserpidine (Schlittler et al. 1955) may be present, but so far only reserpine has been isolated (apart, of course, from known Alstonia alkaloids such as alstonine and its congeners). A detailed investigation of the alkaloids of A. constricta is in progress and further results will appear in a subsequent paper. Preliminary tests carried out by the Division of Animal Health and Production, C.S.I.R.O., with the alkaloid from A. constricts and authentic reserpine showed general similarity in pharmacological action.