Contemporary Cattell-Horn-Carroll (CHC) theory of cognitive abilities has evolved over the past 20 years and serves as the theoretical foundation for a number of current cognitive ability assessments. CHC theory provides a means by which we can better understand the relationships between cognitive abilities and academic achievement, an important component of learning disabilities identification and instructional planning. A research synthesis of the extant CHC cognitive-achievement (COG-ACH) research literature is reported. Systematic and operationally defined research synthesis procedures were employed to address limitations present in the only prior attempted synthesis. Nineteen studies met the criteria for inclusion, which yielded 134 analyses. The 134 analyses were organized by three age groups (6-8, 9-13, and 14-19) and by four achievement domains (basic reading skills, reading comprehension, basic math skills, and math reasoning). The results reveal a much more nuanced set of CHC COG-ACH relations than was identified in the only prior review because of (a) breadth of cognitive abilities and measures (broad vs. narrow), (b) breadth of achievement domains (e.g., basic reading skills and reading comprehension vs. broad reading), and (c) developmental (age) status. The findings argue for selective, flexible, and referral-focused intelligence testing, particularly in the context of emerging Response to Intervention (RTI) assessment models. The results suggest that narrow CHC abilities should be the primary focus of instructionally relevant intelligence testing. Furthermore, the finding that more than 90% of the available research is based on the Woodcock-Johnson Battery argues for significant caution in generalizing the findings to other batteries. CHC-based COG-ACH research with other intelligence batteries is recommended. (Contains 2 tables, 1 figure, and 15 footnotes.)