Simulations and empirical findings justified the estimation of sterility by age in many African countries where the prevalence of sterility has not been measured previously. Simulations indicated that age-specific sterility rates between ages 20 and 44 may be obtained from populations that use contraception, as long as the rates of contraceptive use and contraceptive efficacy do not exceed specified limits, and the sample size is at least 1,500 cases. In Botswana, Kenya, and Zimbabwe contraceptive practice has become so prevalent, that measures of sterility were deemed to be biased when all women were included in the samples analyzed. The prevalence of sterility varied markedly across selected African countries, and was high relative to levels prevailing in populations with little disease. Prevalence of sterility was highest in Cameroon and lowest in Burundi. In Cameroon and Sudan sterility before age 35 appeared to have declined slightly from the World Fertility Surveys around 1980 to the Demographic and Health Surveys around 1990. In Ghana, Kenya, Nigeria, and Senegal there was evidence of a decline in sterility during the 1980s.