This study utilizes data from 47 Demographic and Health Surveys in developing countries to examine levels, trends, and differentials in women’s inability to bear children. Five principal measures were used in the analysis on infertility: childlessness, primary and secondary infertility, self-reported infecundity, and indications of secondary infecundity. In addition, levels of sexual experience, pregnancy, and live births were measured. Overall, by age 45 to 49, only 3 percent of sexually experienced women have not had a birth. Seventeen percent of women age 15 to 49 report themselves as infecund. In this study, a woman is considered secondarily sterile if she has not had a child in the past five years, although she was continuously married and did not use contraception during that period. Secondary sterility is most common in sub-Saharan Africa. The study estimates that in 2002, more than 186 million ever-married women of reproductive age (15 to 49) in the developing countries (excluding China) were infertile because of primary or secondary infertility. This number represents more than one-fourth of the ever-married women of reproductive age in these countries. However, using comparable data, the study shows that infertility, both primary and secondary, has declined in most countries. There is no obvious pattern to changes in the levels of infertility in the countries most affected by HIV. Finally, the study examines some of the consequences and coping mechanisms of couples affected by infertility.