Using the standardization sample from the NEPSY, confirmatory factor analysis was conducted to examine the factor structure for ages 5 through 12 of the NEPSY sample, as well as for the younger (5 to 8 years, n=400) and older (9 to 12 years, n=400) age bands, to explore possible differences in test structure at different developmental epochs. Using four standard fit indices, results indicated that a 5-factor model was less than adequate for the entire sample and produced negative error variance for the younger and older age groups, making any solutions for the two subgroups inadmissible. A 4-factor model without the Attention/Executive Function subtests produced satisfactory fit statistics for the entire sample and the younger group, but did not fit the data as well for the older group. A 1-factor model did not fit well for the full sample. These results indicated that the structure for the NEPSY is not invariant across development, with the 4-factor model best fitting the data for the younger age group and for the entire school-age sample.