This paper attempts to measure the levels of infertility and low fertility and sterility in Africa. In defining the measures, the words "fecundity" and "infecundity" are used to refer to the quantitative study of phenomena directly related to the presence or absence of procreation of children in a population or subpopulation. Similarly, fertility and infertility are used to describe the capacity or inability to procreate. Infertility may be voluntary when couples decide not to procreate. Such a state is defined as low fertility or limited fertility. 4 types of sterility resulting from biological incompatibility are identified: 1) total; 2) secondary (often from medical/physical or psychological problems); 3) partial (inability to have further children after having at least 1); 4) temporary (excluding periods of infecundity but including the menstrual cycles). The author proposes measures of natural fertility and demonstrates that fertility levels in Africa are well below the natural level considered as a medium world figure: 12 children for couples not using contraception. In examining the causes of infertility among African populations the author proposes the main reasons as polygamy, duration of veneral diseases, climatic, ecological, health customs and sexual taboos, and higher than normal sterility among certain ethnic groups. Sterility is defined as a risk. Different measures of sterility may be arrived at by recourse to probability calculus. The technique developed by M. Louis Henry is considered the best measure of sterility. This method is applied to Guinea data for 1954-55 and the Rungwe region in Tanzania for 1967. Other methods of calculating sterility for women aged 15-49 from the number of live births are also described. (author's modified)