This report provides an overview of methods of evaluating the impact of family planning programs in developing countries, with a discussion of their strengths and weaknesses. The focus is on estimation of program impact on fertility rates, though other potential outcome measures, such as maternal and child health, are also discussed. The first section sets the context of recent debates over the effectiveness of family planning programs. The following sections deal with methods of analysis and data requirements for simple standardization of fertility rates for before-and-after comparisons, quasi-experimental designs and multivariate analyses of survey data, and components models for simulating impacts. The tradeoff in designing evaluations is between the difficulty and expense of the data collection and analysis and the reliability of inferences about program impact, since the more reliable and plausible methods demand data not routinely available in countries. The last section discusses the need for estimates of marginal program effectiveness as well as average effectiveness, for resource allocation decisions. (Author/NB)