An intensive exploration of the behavior of pentaquine (SN 13,276) in experimental animals and in human beings has been in progress for over a year. Study of this new antimalarial agent has included evaluations of (1) antimalarial activities in the avian host, (2) pharmacologic and toxicologic properties in lower animals and in man and (3) prophylactic and curative activities in human infections due to Plasmodium vivax. These investigations have been carried out in civilian establishments under the sponsorship of the Committee on Medical Research of the Office of Scientific Research and Development and in various Army installations. The present report is a brief outline of the pertinent conclusions drawn from these studies. CHEMICAL FORMULA AND PREPARATION Pentaquine (SN 13,276) is 6-methoxy-8-(5-isopropylaminoamylamino)-quinoline. It is prepared by condensation of 6-methoxy-8-aminoquinoline with 5-isopropylaminoamylchloride. In all the laboratory and clinical tests, pentaquine has been used in the form of its diphosphate (75.5 per cent