Three explanations regarding the prediction that early career success will moderate the relationship between cognitive ability and career attainment are presented along with an empirical examination of this issue. Using longitudinal data provided for 156 managerial, professional, and technical employees, significant moderating effects for an age-graded index of early career success were observed. The relationships between two measures of cognitive ability and later career job level were stronger for individuals identified as below average with respect to early career success than for their above average counterparts. These results agree with the proposition that the acquisition of knowledge, skills, and information is particularly dependent upon cognitive ability for inhviduals competing without the advantages associated with early career signals of high potential.