Use of complementarity as a deliberate and necessary program evaluation strategy is discussed. Quantitative and qualitative approaches are viewed as complementary and can be integrated into a single study. The synergy that results from using complementary methods in a single study seems to enhance understanding and interpretation. A review of the literature on mixed method designs reveals that many researchers recognize the value of complementary approaches. Complementarity in program evaluation ensures that outside perspectives, such as skill acquisition and achievement of cognitive objectives, are connected with inside perspectives, such as the meaning that actors assign to different situations. When used as a deliberate program evaluation strategy, complementarity capitalizes on the strengths of quantitative and qualitative research methods to provide enriching explanatory and interpretive meaning to the findings. There is a 17-item list of references. (SLD)