A study designed to examine biological, sociological, and early maturational correlates of intelligence collected data prospectively, from birth to 15 years of age, on a sample of 987 black children. Multiple indicators of eight independent and three dependent variables were tested in a structural equation model. Altogether, clear sex differences appeared in the relationship between verbal/spatial IQ at 7 years of age and achievement at age 15. For males, only verbal IQ was positively linked with achievement; for females, both verbal and spatial IQ were positively linked, with spatial IQ showing the stronger effect. With regard to early influences on verbal IQ, both biological and environmental factors were significant for females; only environmental factors were significant for males. However, biological factors were more significant for males in relationship to spatial IQ. Concerning total effects on achievement, socioeconomic factors were stronger than other variables for both sexes, although biological influences were more significant for females. These findings supported literature indicating the relatively more symmetrical development of the left and right cerebral hemispheres among females. Data also supported evidence of earlier development of right hemispheric capacities among black females, although the reverse relationship has previously been found with white samples. (Directions for future research are suggested.) (Author/RH)