All the subtests of the first Spanish language version of the NEPSY were administered to a sample of 415 children aged 3 to 12 years old: 193 boys and 222 girls. For statistical analysis, the sample was divided into two groups: one comprising 98 children aged 3-4, and the other 317 children aged 5-12. First, the adjustment of the distribution of the different items of this Spanish version of the NEPSY subtests to the normal curve was checked. The usefulness of these subtests to assess the level of children's development according to their chronological age was then tested using regression analysis. Finally, we checked that the raw scores on the subtest items of this Spanish version ofthe NEPSY differed significantly between 3 and 4 year olds and between 5 and 6 year olds: in each age pair, the mean scores of the older group increased inaccuracy and decreased in runtime and errors.