An evaluation of data available for estimating fertility and child and adult mortality in Colombia during the past 3 decades, and estimation of levels and trends of fertility and mortality using that data (1951-1977). The data sources include census records (1951, 1964, and 1973), vital registration records, and sample surveys. Each source is evaluated for irregularities and completeness of coverage. The following sample surveys are described in some detail: 1) The 1965 National Morbidity Survey (data not used for this study because published tabulations do not permit application of consistency tests), 2) The 1969 National Fertility Survey, 3) The 1976 Colombian Fertility Survey (part of the World Fertility Survey), 4) The 1978 National Household Survey, and 5) The 1978 Contraceptive Prevalence Survey. Drawing on combinations of these various data sources, estimates of mortality and fertility levels and trends were derived. A final series of yearly child mortality estimates is derived for 1950-78 and presented in a table. It includes estimates by sex of infant mortality and child mortality (probability of dying by age 5). These estimates show a 40% decline in infant mortality between 1950 and 1964 (from 150 to 85 deaths/1000 births) and a 28% decline from 1964 to 1978 (to 64 deaths/1000 births). The total decline in infant mortality over the entire period was 57%. The decline in child mortality over the same period was 54%. Tabulated final yearly estimates of adult mortality, in terms of the expectation of life at birth and at age 5, also show a decline. Expectancy at age 5 increased by 10% for males and 11% for females between 1950 and 1964 (from 43.7 to 53.1 years for males, 46.7 to 56.4 years for females). Estimates of adult mortality for 1964-1978, said to be of uncertain quality because of irregularities in the 1973 census, were derived from a life table fitted to adjusted age specific mortality rates. These estimates show an increase in life expectancy at age 5 of 5% for males and 6% for females. Life expectancy at birth in 1973 was 58.1 years for males and 61.7 years for females. Existing estimates of fertility indicate a fairly constant rate of 6.7 or 6.8 children per woman until 1964 or 1965. Thereafter the fertility rate fell to about 5.1 or 5.2 children per woman in 1973, and to 4.2 in 1978. Yearly estimates of total fertility indicate a 40% decline in total fertility over 15 years. Over the same period, "ever use" of contraception was reported to increase from 33% of ever married women in 1969 to 59% in 1976. The report contains numerous tables and figures presenting data from the sources described, and derived estimates of fertility and mortality.