This study quantitatively reviewed aptitude-treatment interactions (ATIs) in the training literature to address inconclusive results with regard to their existence and nature. The aptitude investigated was trainee general cognitive ability and the treatment was training program structure. 15 studies were investigated with a primary approach that only included studies that directly examined ATIs. 51 studies were investigated with a secondary approach that involved coding the structure of training in studies that reported a correlation between general cognitive ability and training effectiveness. Correlations were meta-analyzed and compared as a function of structure and type of evaluation criterion. Results indicated that small ATIs exist but that the effects vary in size and nature depending on the criterion. For cognitive criteria structure exacerbated the effects of general cognitive ability. In contrast, for skill criteria structure attenuated the effects of general cognitive ability. However, the effects for skill were not robust--they were confounded with training content. The size and nature of the ATIs suggests it is not worthwhile to tailor the structure of training based on trainees' general cognitive ability.