The purpose of this study is to investigate the relations between aptitude variables and school achievement using a model of ability which allows simultaneous identification of general and specific abilities. A battery of 16 aptitude tests was administered in the 6th grade and course grades were collected in 17 different subject matter areas in the 9th grade (N = 866). For the aptitude tests a confirmatory factor model is fitted with a general factor (G) along with nine orthogonal, residual factors. Some of the residual factors are quite broad (Crystallized intelligence, Gc(1), and General visualization G(1)), but most are narrow factors identified by pairs of tests (e.g., V(1), Ms(1), Num Ach(1), Vz(1), S, and Cs(1)). A model is fitted to the 17 course grades as well. The model includes a general school achievement factor (GENACH) and domain specific achievement factors in areas such as science-mathematics (SCIENCE), social science (SOCSCI(1)), language (LANG(1)) and spatial-practical performance (SPATPR(1)). Relating the latent criterion variables to the latent aptitude variables it is found that some 40% of the variance in GENACH may be accounted for by G and Gc(1). However, larger proportions of variance are accounted for in the domain specific achievement factors and different aptitude factors are important in different domains. It is conclu~ded that differentiation among at least a limited number of broad abilities may be worthwhile.