The influence of age and sex on the performance of children of preschool and school age at tests measuring coordination abilities was examined in the present study. The linearity of motor performance in childhood was also examined. The sample consisted of 64 preschoolers, 62 first graders, 65 second graders, 61 third graders and 61 fourth graders. The Bruininks-Oseretsky Tests of Motor Proficiency were used for measuring the coordination abilities. The results of the multivariate analysis of variance (MANOVA) showed no sex influence at children performance and an important impact of age factor. Finally, there is no linearity at the performance of children aged 8-10 years old. This is not the case for children aged 4-7 years old.