PIP: In Mexico as in many other countries, the demographic transition began with mortality decline. With the great epidemics largely disappearing by the mid-19th century as a result of public health and sanitation measures, the mortality rate stabilized and began an accelerated decline after 1920. Life expectancy at birth was about 30 years in 1900 and declined during the decade of the Mexican Revolution. By the 1980s it had risen to 69 years. Fertility remained at high levels with slight variations until the late 1960s, when it began to decline 50 years after the start of the mortality decline. Government family planning programs intended to reduce the rate of population growth accelerated the fertility decline. Great changes thus affected Mexico¿s population during the 20th century. The total population increased from 14 million in 1900 to 82 million in 1990. Population growth was relatively slow and constant at around 1.3% until about 1910. It accelerated from the 1920s to the 1960s, and the number of children under age 15 increased sharply. Growth rates began to decline and the population to age in the 1970s. By the 1980s, Mexico¿s fertility rate reached an all-time low. The decline of population growth will be more apparent when the first cohorts of reduced size reach the peak fertility years shortly after 2000. Mexico¿s demographic transition is not yet complete. The evolution of fertility will be decisive in future demographic dynamics.