In a previous systematic review, the author proposed that adaptation to learners' cognitive and learning styles (CLSs) could improve the efficiency of computer-assisted instruction (CAI). In the present article, he questions that proposition, arguing that CLSs do not make a substantive difference in CAI. To support this argument, the author performed an updated systematic literature search, pooled new findings with those from the previous review, and reinterpreted this evidence with a focus on aptitude-treatment interactions. (An aptitude-treatment interaction occurs when a student with attribute 1 learns better with instructional approach A than with approach B, whereas a student with attribute 2 learns better with instructional approach B).Of 65 analyses reported in 48 studies, only 9 analyses (14%) showed significant interactions between CLS and instructional approach. It seems that aptitude-treatment interactions with CLSs are at best infrequent and small in magnitude. There are several possible explanations for this lack of effect. First, the influence of strong instructional methods likely dominates the impact of CLSs. Second, current methods for assessing CLSs lack validity evidence and are inadequate to accurately characterize the individual learner. Third, theories are vague, and empiric evidence is virtually nonexistent to guide the planning of style-targeted instructional designs. Adaptation to learners' CLSs thus seems unlikely to enhance CAI. The author recommends that educators focus on employing strong instructional methods. Educators might also consider assessing and adapting to learners' prior knowledge or allowing learners to select among alternate instructional approaches.