Factor analyses have been computed in samples of white male and female and black male and fe male students for the same 16 cognitive variables at grade levels 5, 7, 9, and 11. Samples for each of the four independent groups remained constant at the four grade levels. The latent roots as analyzed in three ways show a clear but small increase in the number of common factors during this time period, particularly for the white groups. Rotated factor loadings also support the differentiation hypothesis. For the white males, who showed the clearest evi dence for differentiation of abilities, rotated load ings provide descriptions of the emerging factors. Although the evidence for differentiation is less clear in white females, the emerging factors appear to become identical by the 11th grade. Data for black males and females, which are based on small er Ns, are more ambiguous.