PIP: This work examines the determinants and most important consequences of the Brazilian fertility decline. Brazil's total fertility rate declined from 6.2 in 1940 to around 3.5 in 1985. the decline began in the 1960s and amounted to 45% in about 20 years. The most rapid drop began in the late 1970s, with much of it concentrated in 2 specific periods: 1970-75 and 1980-85. The early period coincided with Brazil's so-called "Economic Miracle", a period of rapid growth accompanied however by deteriorating living conditions for the poorest population sectors. The second period coincided with the international economic crisis of the early 1980s, which was felt more strongly in Brazil than elsewhere in Latin America because of Brazil's greater degree of industrialization and closer integration into the world economy. Most of the fertility decline has been accomplished by use of just two contraceptive methods, oral contraceptives and sterilization, which together account for around 85% of contraceptive usage throughout Brazil. The third most common method, rhythm, accounts for just 6%. No reliable data on abortion are available, but it appears to be a common practice equally accessible to all socioeconomic strata despite greater associated health risks for poorer women. Brazil's fertility transition appears to have been a response to the process of proletarianization and urbanization underway in the country as well as to particular circumstances in the country. The most evident and immediate consequence of the continuous fertility decline over more than 20 years is the change in the age structure of the population. The proportions of children under 5 will decline from 14.4% in 1980 to 9.2% in 2010. The proportion aged 5-14 will decline from 24.5% to 17.4%, while the proportion aged 65 and over will increase from 4.0% to 5.6%. Brazil's recent demographic changes are scarcely reflected in development plans and political and social projects. There is almost no mention of the new demographic dynamics which entail new problems to be faced, but also new and more favorable conditions for overcoming some old problems. Most planners retain a conception of Brazil's population as very young, rapidly growing, and with a constant age distribution. Some promising areas for social investment are health, nutrition, and preschool education for small children; improvement and expansion of the public educational system; and improvement in the quality of the labor force. The growing elderly population will require health services, pensions, and alternative living arrangements for the increased proportion without close relatives. A regional development strategy should be developed to assure that conditions do not deteriorate in any region as demographic changes progress.^ieng