The representativeness, recency, and size of norm samples strongly influence the accuracy of inferences drawn from their scores. Inadequate norm samples may lead to inflated or deflated scores for individuals and poorer prediction of developmental and academic outcomes. The purpose of this study was to apply Kranzler and Floyd’s method for estimating norm block sample sizes via a review of the most prominent, individually administered intelligence tests. A rigorous, double-coding process was used to obtain these estimated sample sizes for 17 intelligence tests (10 full-length multidimensional tests, 4 nonverbal intelligence tests, and 3 brief intelligence tests). Overall, 47% of the tests failed to meet the minimum standard of at least 30 participants per norm block across age groups, and estimated norm block sizes were smallest for elementary school–age children. These results can inform intelligence test selection by practitioners and researchers, and they should be considered by test publishers when developing, revising, and reporting information about their tests.