OBJECTIVE: To calculate the prevalence of developmental coordination disorder at 7 years of age by using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria in a large UK birth cohort. METHODS: Cases of developmental coordination disorder were defined by using data from the Avon Longitudinal Study of Parents and Children, a UK birth cohort. The motor coordination of >7000 children was assessed by using tests that measured manual dexterity, ball skills, and balance. The 5th percentile of the derived Avon Longitudinal Study of Parents and Children coordination impairment score was used to define severe motor coordination difficulties. Data from national handwriting tests and an activities-of-daily-living scale quantified the impact of poor coordination on daily life. Children with known neurologic conditions or an IQ of <70 were excluded. RESULTS: Complete data were available from 6990 children aged 7 to 8 years who attended the coordination session and completed the writing test or activities-of-daily-living scale. One hundred nineteen children met criteria for developmental coordination disorder, resulting in a prevalence of 17 of 1000 children at a mean age of 7.5 years (SD: 2.9 months). An additional 222 children were considered as having "probable developmental coordination disorder" by using broader cut-offs for coordination testing and activities of daily living. There was an increased risk of developmental coordination disorder in families from lower socioeconomic backgrounds, in children with a birth weight of <2500 g, and those born before 37 weeks' gestation. CONCLUSIONS: This is the first study to use strict criteria to define the prevalence of developmental coordination disorder in a representative cohort of UK children. A prevalence of 1.7% is lower than studies that have not taken into account the impact of poor motor coordination on daily living but indicates that poor coordination is an important, and often hidden, cause of disability in childhood.