This study sought to assess the determinants of fertility and of fertility control in Kenya and Lesotho, with particular emphasis on the influence of factors associated with modernization. The study was based on World Fertility Survey data sets from both countries collected in 1977-78. It was hypothesized that the differential use of fertility regulation between these 2 countries in part explains Kenya's higher fertility. However, both countries were found to be natural fertility regimes, with about a 10% contraceptive prevalence rate. Proximate determinants analysis indicated that household fertility was inversely related to both the 1st and 2nd birth intervals, duration of breast feeding and pregnancy wastage, and directly related to fecundity, duration of marriage, and child mortality. Fertility was also directly related to ever-use of fertility control in both countries. About 39% of Kenya's higher fertility could be accounted for by the postpartum amenorrheic variables, while fecundity variables explained 35%. However, the single most important determinant of Kenya's higher fertility than Lesotho's was its lower level of secondary sterility. Mean age at marriage is higher in Lesotho (19 years) than Kenya (17 years). Lesotho women also breast feed their infants about 6 months longer than women in Kenya. Households that regulated fertility were more likely to have higher motivation, greater knowledge of fertility control methods, and know more efficient methods of contraception. Modernization variables, especially education and occupational status, dominated the cultural variables in explaining household variation in the proximate determinants of fertility and determinants of use of fertility control. Wife's education had the most pervasive effect on fertility and tended to reduce duration of marriage, increase knowledge of contraception, and lower family size ideals. - See more at: http://www.popline.org/node/422458#sthash.QhleWHOM.dpuf