The purpose of this study was to examine developmental change associated with mature catching by children in grades K-8. Specifically, we addressed the following research questions: What are the characteristics of individual differences in mature catching development over time? Are differences in developmental growth trajectories of mature catching systematically related to age, sex, or participation in organized sports? The basic design for this study was multi-cohort longitudinal. This design enabled us to examine the association of age, sex, and baseball/softball participation while reducing cohort effects. We tested children?s performance on the catching subtest of the Ohio State University Scale of Intra-Gross Motor Assessment (OSU-SIGMA). More precisely, we tested four cohorts of boys and girls in grades k-8 (N = 340) from 1992 to 2000: 1992 = k-8, 1994 = 2-8, 1996 = 4-8, and 1998 = 6-8. In 2000 we again tested the original kindergarten cohort. The data were analyzed by hierarchical nonlinear modeling. This technique uses slopes and intercepts of children?s catching performances to establish individual growth trajectories. Predictor variables (age, sex, and baseball/softball participation) were then added to the model to provide a clearer understanding of mature catching development. The principal findings were: a) significant differences were found in the mean initial status (intercept) and growth rate (slope) for the cohorts; b) sex differences were observed among cohorts in initial status; and c) no differences were observed for baseball/softball participation.Keyword(s): gender issues, performance, research