This volume is the result of a study conducted by the International Association for the Evaluation of Educational Achievement (IEA) as part of the Six Subject Survey in Science, Literature, Reading Comprehension, English and French as Foreign Languages, and Civic Education. The project was begun in 1966 with the first phase of instrument development lasting unitl 1969, and the second phase comprising the field testing and analysis of data taking place from 1970 through 1973. This report gives an account of the conceptualization, execution, analysis and results of the international science study which was conducted in the following 19 countries: Australia, Belgium (Flemish-speaking), Belgium (French-speaking), Chile, England, FRG (Germany), Finland, France, Hungary, India, Iran, Italy, Japan, Netherlands, New Zealand, Scotland, Sweden, Thailand, and the United States. Apart from studying descriptively the teaching of science and the conditions under which it is conducted in various countries, the overriding thrust of the study attempts to relate factors in the social, economic, and pedagogical domains characteristic of a series of national systems to output factors measured by international tests, covering both cognitive and affective outcomes. These relationships were studied simultaneously at two or three age levels within each country. (JR)