The 1960s marked a turning point in the history of world population growth as the annual rate of increase, which reached 2%, ceased its ascent. Fertility rates have declined sufficiently rapidly to produce lessened growth rates when compared to mortality among 3/4 of the world's population. The maximum growth rate of developing countries occurred about 1960-65, with a value of 2.4% produced by birthrates of about 40/1000 and mortality rates of about 16/1000. The growth rate is now under 2.1%, due to declines of birthrates to 32/1000 and mortality rates to 11/1000. The recent demographic development of 40 developing countries with populations of over 10 million in 1982 is examined in greater detail including 13 African countries, 8 Latin American countries, 4 East Asian countries, and 15 South and West Asian countries. In 1975-80, the total fertility rate was under 4.7 children/woman, while in 1950 it exceeded 6. A regional comparison for these years indicates that fertility in Africa has scarcely changed in 25 years, while the lowest rates, under 4 children/woman, were found in 3 Latin American and 4 East Asian countries in 1975-80. Reasons for the fertility decline in different countries have included higher marriage age, increased use of contraception in situations where the effect exceeded that of lessened durations of lactation, smaller ideal family sizes, and general socioeconomic progress. Among all developing countries, life expectancy at birth has increased from 42 to 55 years since 1950, but the differences between countries remain great, with almost all African countries, and most South and West Asian countries having life expectancies under 50. Infant mortality rates declined significantly in most of Latin America, but remain very high in Africa and South Asia. Improvements in mortality apparently do not correlate as well with economic development per se as with improved maternal and infant health care, improved water supply, and improved nutrition. A graphic representation of the declines in fertility and mortality in the 40 countries indicates that they are closely related.