This study documents the development of hand and upper-extremity function in young children who have cerebral palsy (CP) with upper-extremity involvement using longitudinal data. Assessments of hand function and the quality of upper-extremity movement were conducted on 29 males and 22 females (mean age 36.2 months, SD 10.6; age range 16 to 60 months at baseline) and on four other occasions over 10 months. Linear mixed effects modeling was used to estimate average developmental curves and the degree of individual differences in the patterns of development which were conditional on the body-site distribution of CP and severity of impairments. Results indicate that hand function in this clinical population develops differently from overall upper-extremity skills with declines in function in upper-extremity skills being more common and pronounced among older children. However, there is substantial interindividual variation. Distribution of CP and severity of impairments were significant predictors of development. Results are discussed in terms of their clinical implications.