The maximal split-half coefficient is computed by calculating all possible split-half reliability estimates for a scale and then choosing the maximal value as the reliability estimate. Osburn compared the maximal split-half coefficient with 10 other internal consistency estimates of reliability and concluded that it yielded the most consistently accurate estimate of reliability across the conditions explored. In this simulation study, the authors demonstrate that the maximal split-half coefficient can, under some conditions, badly overestimate reliability because of capitalization on chance and under other conditions appreciably underestimate reliability. Cross-validation can correct the former problem. A difficulty with the cross-validated coefficient is that it is a relatively inefficient estimator of reliability. (Contains 5 tables and 4 figures.)