Maternity histories from residents of a Pacific Island society, Tokelau, and migrants to New Zealand, are analysed using life table techniques. Inter-cohort differentials in patterns of family formation were found in the total Tokelau-origin population. The process of accelerated timing and spacing of pregnancies was more pronounced among migrants who tended to marry later, be pregnant at marriage, have shorter inter-pregnancy intervals at lower parities and to show evidence of family limitation occurring at higher parities. These results point to the significance of changing patterns of social control on strategies of family building.