PIP: The components method, utilizing census data from the 1950-1980 censuses and provisional data from the 1990 census, was used to project the Mexican population through 2025. The basic assumptions were that the mortality decline would slow as higher life expectancies at birth were achieved, as in the developed countries; that fertility would continue to decline until reaching replacement level around 2015; and that net international migration would continue at a constant rate. Mexico is at an advanced stage in its demographic transition. Between 1950-55 and 1970-75, the crude death rate was cut by nearly half, from 16.6 to 8.9/1000. The crude birth rate subsequently declined by 30% between 1970-75 and 1990-95, from 42.7 to 27.9/1000. By 2025, the annual growth rate is expected to decline by 60% relative to the rate in 1990-95. The age distribution has changed due to changes in demographic variables. The proportion under 15, 43.0% in 1950, 45.6% in 1960, and 46.7% in 1970, dropped to 38.0% in 1990 and is projected at 23.3% in 2025. The population 65 and over was 4.2% in 1950, declined to its minimum of 3.7% in 1970, and is projected at 8.5% for 2025. The population of working age (15-64 years) accounted for 52.8% in 1950, 58.3% in 1990, and is projected at 68.2% in 2025. The median age is projected to increase from its minimum of 16.6 in 1970 to 32.0 in 2025. The age structure of the population will be beneficial during most of the projection period because of the declining dependency ratio, but the needs of the older population will require higher priority in coming years. The demand for health, education, and other services for children will continue to moderate as the age structure changes.