The present research was designed to examine more extensively the effects of bilingualism on the intellectual functioning of children and to explore the relations between bilingualism, school achievement, and students' attitudes to the second language community. The subjects were 10-year-old school children from six French schools under the jurisdiction of the Catholic School Commission of Montreal. The testing took place in the classroom and was divided into five sessions of 1 hour each, spaced about a week apart. All instructions to the children were given in French by native speakers of French, except for the test of English vocabulary which was administered by a native speaker of English. Verbal and nonverbal intelligence tests and measures of attitudes to the English and French communities were successfully administered. Contrary to previous findings this study found that bilinguals performed significantly better than monolinguals on both verbal and nonverbal intelligence tests. Several explanations are suggested as to why bilinguals have this general intellectual advantage. It is argued that they have a language asset, are more facile at concept formation, and have a greater mental flexibility. The results of factor analyses applied to the data supported the hypothesis that the structures of intellect for the two groups differ. The bilinguals appear to have a more diversified set of mental abilities than the monolinguals. The correlations of the attitude measures with other variables are also discussed.