The International Association for the Evaluation of Educational Achievement (IEA) conducted a six-subject survey to examine achievement in 23 nations with 15 different languages of instruction. The technique used was cross-sectional, with sampling at three different educational levels. In addition to achievement testing in science, reading comprehension, literature, French, English, and civic education, extensive information on input and process variables was collected from students and school personnel. This report discusses selected findings from the analyses of between-country differences in achievement as well as from within-country analyses of the relationships between school outcomes and the input and process variables. (AA)