The study examined the correlates of behaviour of 102 aggressive and 103 prosocial boys, selected by peer and teacher ratings, from grades 5 and 6 in 10 schools in urban Kingston and St. Andrew. The children were given in-depth questionnaires, school achievement tests (WRAT) and verbal ability tests (Peabody Picture Vocabulary Test). Their parents were also given questionnaires. Interobserver and test-retest reliabilities were established for all questionnaires and tests. Interviewers were unaware of the boys' group. The aggressive group was significantly older (mean 11.4 years) than the pro-social boys (mean 11.1 years; t-test p,0.01). The aggressive group had significantly lower scores on both the number of possessions and the housing rating (proxies for socio-economic status), they showed significantly lower scores on spelling, arithmetic, reading and verbal IQ, and considered themselves less bright than the pro-social boys. Preliminary analyses indicate that, as expected, the aggressive boys fought more and used knives in fights more compared with the pro-social boys. They reported receiving significantly more punishments at home. The aggressive group indicated that they saw significantly more family quarrels, threats between family members and family fights. All differences remained significant when socio-economic status was controlled in analyses of covariance except that the differences in the arithmetic scores was no longer significant. Many of these patterns are similar to those reported elsewhere.