Patients with rickets frequently are seen by orthopaedic surgeon with complaints of growth disturbance, limb deformity, weakness, and multiple fracture. Among them, bow leg deformity is the most common and difficult orthopaedic problem. In growing child, however, if effective tretment is given sufficiently in early age and early disease process, the deformities usually correct spontaneously and there is little need for orthopaedic treatment other than careful observation. The orthopaedic treatment may be required to correct deformities that cannot be expected to improve with growth. A clinical study was done for 11 cses of rachitic bow leg deformity who were treated at the department of orthopaedic surgery, Catholic medical College and Center from Jan. 1978 to Dec. 1981. Results obtained were as follows: 1. The most common patients age group was in 1 to 2 years of age and there was no sexual difference. 2. Associated deformities with rachitic bow leg were rachitic rosary (5 cases), double wrist (3 cases), coxa vara (1 case), and Harrison's groove (1 case). 3. Low Ca * P solubility product, below the level of 30 (mg/dl)² suggested active form of rickets in all cases. 4. Laboratory values such as Ca * P solubility product and alkaline phosphatase improved at 3 weeks after administration of vitamin D in 7 cases, 3 at 6 weeks, and no improvement in one case even at 6 months after treatment. 5. Six months after treatment, the average amount correction of tibiofemoral angle was 9° (43.7% of initial angle) in group 1, 13.3° (47.0%) in group II, 4.9° (29.6%) in group III, and 3.3°(25.6%) in group IV. 6. Through this study it is suggested that the more growth correction of the rachitic bow leg deformity in a younger child below the age of 2 is obtained with growth by treatment, whereas a little or no growth correction can be expected after the age of 3 or 4 years.