The predictive validity of assessment procedures can be increased by adding predictors to the prediction supplied by general ability tests. Out of Jensen's early work comes the suggestion of focusing on the cognitive ability short-term memory (STM). Meta-analysis convincingly shows high predictive validities of STM tests for various criteria, but memory tests and g are not independent, but substantially related. So, the question is whether STM tests show incremental validity for school achievement measures over the validity supplied by g. We used five large samples of school children from East-Africa (total N=3121) who took a battery of 15 cognitive tests including 2 STM tests and regressed school achievement measures on g and STM. The most powerful single predictor of the criteria clearly is g. In general STM scores add very little to the predictive validity supplied by g. In many cases there is no incremental validity, the incremental validity decreases, or it increases when STM is weighed negatively. It is concluded that for African children short-term memory tests show very little promise in adding to the predictive validity supplied by g. © 2004 Elsevier Ltd. All rights reserved.