Significant conclusions are presented of the application of a cost-benefit model of family planning in Rwanda. The model and computer programs used were developed by the Research Triangle Institute and financed by the US Agency for International Development. The UN Population Fund participated in the project, which represented the 1st application of the model in Africa. Rwanda's population growth is among the most rapid in the world. The population has increased from about 2 million in 1950 to over 7 million in 1989. The model is composed of 2 parts, the 1st of which discloses the scope of the family planning program and its impact on population growth. The resulting projections are the basis for the 2nd module, the actual cost-benefit analysis which measures the impact of family planning on sectorial expenditures and analyzes the costs and benefits of the program in different sectors. The sectors of health, education, and agriculture are included in this presentation. 2 hypotheses about population growth are included; the 1st assumes the current family planning program and the 2nd assumes no family planning program. The model commences with population and family planning data for 1981. Data through 1989 represent observed rates and those for 1990-2011 are target rates. Only modern family planning methods are included in the model. The prevalence rate for modern methods increased from nearly null in 1981 to 5.3% in 1989 and following current trends is projected at 34.8% in 2000 and 46.8% in 2011. The total fertility rate was 8.6 in 1981 and is projected at 5.5 in 2000 and 4.7 in 2011. The total population is projected at 13.2 million in 2011 with a family planning program or 17.7 million without one. Health expenditures in the final year of the projection would be 41% greater without a family planning program. The family planning program would permit a reduction in the number of children to be educated of over 1 million students, a 54% decrease, assuming that the rate of attendance would be the same with or without a family planning program. The amount of money saved in 2010 with a family planning program would exceed the entire 1988 government budget for education. Although the total food supply would be greater without family planning because of the larger number of workers, per capita food consumption would be less because of the much greater number of consumers. Per capita food consumption in the final year of the projection would be 23% greater with a family planning program than without it. Considering the costs and expenses in the 3 sectors, the country would realize a net savings of 221.8 billion Rwandan francs over a period of 30 years. The ratio of benefits and costs in 2010 in the 3 sectors was estimated at 15.8. For each Rwandan franc invested in the family planning program, Rwanda will save 15.8 francs in the time period considered.