This paper examines the concepts of program monitoring and program evaluation in the literature, and offers working definitions based on two dimensions of measurement: focus (what questions are addressed) and timing (how often the measures are taken). Focus can be on inputs to the program or outcomes from it; timing can be one-shot or continuous. Continuous measures are here considered to be monitoring--"input monitoring" if the measures are on inputs, "impact monitoring" if they are on outcomes. One-shot measures are considered to be evaluation--"process evaluation" if it measures inputs, "impact evaluation" if it measures outcome. The paper further defines program monitoring as part of the evaluation process, and notes that program evaluators must work with project managers in making informed decisions, avoiding information overload, and implementing and monitoring effective programs. The different definitions of program monitoring by Rossi, Freeman, and Wright by the Evaluation Research Society, by the World Bank; by J. Wholey, and by the International Statistical Program Center are considered and compared. (JGL)