This pilot study investigates the effects of aquatic therapeutic exercise on lower-extremity range of motion, gait, balance, and functional mobility in children with juvenile arthritis. Eleven patients, aged 4-13, with lower-extremity joint involvement, diagnosed as functional class I-III, completed a 6-week program of aquatic exercise aimed at increasing lower-extremity range of motion and strength. Despite the small sample size and short duration of the study program, significant improvement was noted in external and internal hip rotation, bilaterally (p < 0.05). Improvement was noted in the median scores for most other parameters; however, these did not reach statistical significance. Aquatic exercises performed in a group setting can serve as an enjoyable and beneficial part of therapy for children with arthritis. Further investigation is recommended to determine fully the effects of aquatic therapeutic exercise on mobility and fitness in children with juvenile arthritis.