This paper analyses regional fertility patterns in Kenya since 1989 using data from the four Demographic and Health Surveys of 1989, 1993, 1998 and 2003, and a consistent set of 21 regions. The impacts of late and non-marriage, contraceptive use, sterility and postpartum non-susceptibility on fertility in each region are quantified using the model of the proximate determinants of fertility developed by John Bongaarts. The model is modified to take account of the impact of non-marital childbearing and secondary sterility. Substantial and persistent regional differentials in fertility are identified. Generally, fertility is lowest in urban areas and in rural areas in the centre of the country. It is higher in both coastal and western areas. The pattern of increasing contraceptive use and a rising age at marriage offsetting the impact of shorter durations of breastfeeding as modernisation progresses is only found in a small number of regions in Central and Eastern Provinces, and in Nairobi. Elsewhere a variety of demographic regimes is observed, some associated with fertility decline, others associated with constant or even increasing fertility. There are differences between the experiences of Nairobi and Mombasa, the two largest urban areas, with Mombasa’s low fertility being associated with none of the major proximate determinants