Children with hemiplegic cerebral palsy may develop differences in limb length; when severe, limb length equalization may be recommended. Serial bone ages are necessary to predict when to perform equalization procedures. By convention, the left hand is always used to determine bone age. There is little information regarding the effect of hemiplegia on bone age. It was postulated that children with left hemiplegia will show a delay in bone age compared with those with right hemiplegia, and it was the purpose of this study to review this question. A retrospective review of 38 children (27 boys, 11 girls) with hemiplegic cerebral palsy between 1980 and 2000 was performed. The hemiplegia involved the right side in 21 and the left side in 17. The hand-wrist bone age was determined by one observer using the Greulich and Pyle atlas. The paired t test was used to analyze for differences between bone age and chronologic age. There was no difference between the average chronologic age (12.0+/-3.5 years) and average bone age (12.0+/-3.7 years) (P=0.83). There was no difference between the chronologic and bone age for either those with right hemiplegia (P=0.65) or left hemiplegia (P=0.87). It is not necessary to obtain radiographs of both hands in children with hemiplegia during routine monitoring of limb length discrepancies.