As a background to the I.B.P. investigation of Kaul village on Karkar Island, a study of the demography of the whole population of Karkar was undertaken. The structure of the population of Karkar is described and an account given of the patterns of movement between the various components of the island population. The fertility of the Karkar population was quite high and significantly greater than that of families studied at Lufa in the Eastern Highlands. The reproductive age-span of Karkar women appeared to be longer than that of the Highland women at Lufa, although Karkar women married later. A significantly greater proportion of Karkar women were lactating in the 40 49 year age cohort than in the women studied in the Highlands. The mean number of living children per male was also significantly higher on Karkar than in the Highlands. The mortality rates from Karkar are also described.