We investigated sex effects and the effects of educational attainment (EA) on the covariance structure of the WAIS-III in a subsample of the Spanish standardization data. We fitted both first order common factor models and second order common factor models. The latter include general intelligence (g) as a second order common factor. The results indicate that sex differences in means are due mainly to the WAIS-III factors Working Memory (WM) and Perceptual Organization (PO), rather than to the second order g factor. In treating EA as a predictor of the first common factors, we found that EA explained a significant, but clearly varying, amount of variance in the 4 first order common factors. Differences in explained variance over sex were very small. Treating EA as a predictor in the second order common factor model, we found that EA predicted g and first order factor Verbal Comprehension (VC). The relationships between PO, WM, and Perceptual Speed (PS) and EA are mediated by g. In treating EA as a dependent variable, we found that VC and PS were the only significant predictors of EA in the first order common factor model. In the second order common factor model, the same result was obtained. While VC and PS were significant predictors of EA, the second order factor g, and PO and WM were not. The results are of theoretical interest in the light of the Ankney-Rushton paradox, and the role of g in educational attainment.