Objective: To determine the effects of intensive task-specific strength training on lower limb strength and functional performance in children with cerebral palsy. Design: A nonrandomized ABA trial. Setting: Sydney school. Subjects: Eight children with cerebral palsy, aged 4-8 years, seven with diagnosis of spastic diplegia, one of spastic/ataxic quadriplegia. Intervention: Four weeks of after-school exercise class, conducted for one hour twice weekly as group circuit training. Each work station was set up for intensive repetitive practice of an exercise. Children moved between stations, practising functionally based exercises including treadmill walking, step-ups, sit-to-stands and leg presses. Main outcome measures: Baseline test obtained two weeks before training, a pre-test immediately before and a post-test following training, with follow-up eight weeks later. Lower limb muscle strength was tested by dynamometry and Lateral Step-up Test; functional performance by Motor Assessment Scale (Sit-to-Stand), minimum chair height test, timed 10-m test, and 2-minute walk test. Results: Isometric strength improved pre- to post-training by a mean of 47% (SD 16) and functional strength, on Lateral Step-up Test, by 150% (SD 15). Children walked faster over 10 m, with longer strides, improvements of 22% and 38% respectively. Sit-to-stand performance had improved, with a reduction of seat height from 27 (SD 15) to 17 (SD 11) cm. Eight weeks following cessation of training all improvements had been maintained. Conclusions: A short programme of task-specific strengthening exercise and training for children with cerebral palsy, run as a group circuit class, resulted in improved strength and functional performance that was maintained over time.