It is easy to observe that meta-analysis is quickly establishing itself as useful tool of the social sciences. Perusal of representative journals confirms that meta-analysis has been applied in various ways to diverse literatures. It is imperative, therefore, that reviewers, publishers, consumers, and critics of these reviews be best informed about the method. It is especially important to clarify exactly what the term "meta-analysis" refers to. This article proposes a clarification in two ways. First, meta-analysis is compared to and distinguished from other methods of research integration that preceded it. Second, five different types of meta-analytic method are distinguished by their purposes (for scientific criticism or for literature review) or by their methods (using combined probability, using tests of homogeneity, or using estimates of population variation). (Author/BW)