This study examines twenty-four cases of amok, believed the largest number of cases ever collected. They were observed in Sarawak, East Malaysia. They occurred in all indigenous groups in Sarawak, excluding the Chinese, such as Malay, Sea Dayak, Land Dayak, Kayan, Punan and Melanau at frequencies more or less following the proportion of these groups in the total population. No differences were found according to religion, the Malay being Muslim and the other groups either predominantly Christian like the Iban or animistic. Only slight diminution in the frequency was observed from 1954 to 1968. The education level of the amok runners was much lower than that of the average population. The weapons used were those immediately at hand be it parang (short sword), ax, sticks, knives, guns, bare hands or a lorry. The classical four stages were largely present: (a) brooding and withdrawal, (b) homicidal paroxysm, (c) continuation of homicidal behaviour until killed, restrained or falling into stupor of exhaustion, (d) complete or partial amnesia. While in 14 no motive could be ascertained, insult, jealousy and paranoid ideation was present in the others. Both family history of mental illness and personal psychiatric history were predominant. All cases fell into accepted diagnostic categories from organic and endogenous psychosis to neurosis and behaviour disorder.