The objective of the study was to evaluate the effectiveness of modified constraint-induced movement therapy in young children with hemiplegia. It was a single-case experimental design using children as their own controls. Assessment was at entry to the study and subsequently at 4-weekly intervals. A 4-week baseline period with no hand treatment, controlling for maturation, was followed by a 4-week treatment period and a second 4-week period with no hand treatment to measure carry-over. Treatment consisted of twice-weekly 1-hour sessions of structured activities with a therapist and a home programme for non-treatment days. Only verbal instruction and gentle restraint of the unaffected arm were used to encourage use of the affected arm. Nine children (six males, three females; median age 31mo, age range 21 to 61mo) presenting with congenital spastic hemiplegia (five right side, four left side) were involved in the study. Changes in hand function were evaluated with the Quality of Upper Extremity Skills Test. Improvement was seen throughout the study with statistical significance, using the Wilcoxon signed rank test, of 0.01 immediately after treatment. Results of this pilot study suggest that this modification of constraint-induced movement therapy may be an effective way of treating young children with hemiplegia. Future work is planned to consolidate and develop these results.