Presents a system for evaluating rural water-supply projects. Stresses clarifying project design and identifying promising evaluation approaches. Though field work was conducted in Upper Volta, in Western Africa, the evaluation plan is designed to be generally applicable to rural water projects. Sections of the paper provide a prototype logical framework for rural water supply projects, specifying goals, purpose, outputs, and assumptions. General requirements for an information system to support decisions in the Upper Volta Water Supply Project identify key decisions, decision-makers, and decision criteria. Approaches to measurement in an information system for the Upper Volta Project note discrete methods for securing evidence on specific types of change, including a critique of some standard data-collecting methods. Recommends project management, project information system, methodological issues, summative evaluation. Appended are a previously published article entitled "Maximizing the Power of Causal Investigation: The Modus Operandi Method," and a brief discussion of two attempts at estimating diarrhea incidence without medical examination.