An analysis of data from the 1978 National Fertility Survey, from the 1987 census, and from the 1991 Demographic and Health Survey gives the fertility level and fertility trends in Cameroon and the determinants of fertility. Total fertility fell 11% between 1978 and 1991 from 6.5 to 5.8. This decline in fertility was largely a result of the decline in fertility in Cameroon's 2 largest cities, Yaounde and Douala, from 5.3 to 4.4. Rural women and women with no formal education had the highest total fertility in 1991 (6.29 and 6.2, respectively). The mean ideal family size in 1991 was high (6.8), which may explain the low prevalence of current modern contraceptive use (4.2%). 80.3% used no family planning method at all. In 1991, 10.3% of women in Cameroon suffered from primary infertility. 6.5% and 8.5% of women have 1 and 2 children, respectively, and have secondary infertility. Primary infertility is highest in rural areas (11% vs. 3.3-9.6%) and in the eastern and southern regions (40% and 20%, respectively vs. 3.2-6.4%). Postpartum abstinence and breast feeding lead to a median duration of 16 months of protection from conception. Postpartum abstinence and breast feeding contribute to more than 40% of the reduction in fertility. Increased marriage age (mean age at marriage = 18.4 in 1978 and 19.6 in 1991) contributes to 17% of the reduction in fertility. Primary infertility contributes to 11%. Contraception currently contributes only marginally to fertility decline. The proximate determinants of fertility (e.g., contraception) will determine the future of fertility in Cameroon.