The direction and magnitude of sex-related differences in science attitude and achievement have been topics of conjecture and research. Reported here are findings of a quantitative synthesis of completed research relating to these issues. A comprehensive literature search revealed 83 "articles" (journal publications, books, unpublished reports, dissertations), standardized tests, and large-scale national/international studies providing data on sex differences and reporting either statistics from which "Effect Size" could be derived or information which could be tallied into "Vote Scores." (Vote scores contain less information than Effect Sizes, but their use permitted inclusion of all studies in which sex comparisons were made, even though detailed statistics were lacking.) Data from 298 independent samples provided 613 Effect Sizes and 132 Vote Scores which were analyzed using a general linear model approach to analysis of variance, controlling for intercorrelations among variables. Results indicated that sex differences in attitude/achievement were smaller than generally assumed, but when they did occur, with few exceptions, tended to favor males. Data on sex differences in attitude are discussed within the context of a large number of school, individual, and methodological variables including academic discipline, age, instrument reliability, country of sample, socioeconomic status, geographic region, age, and dimension of attitude. (Author/JN)