The purpose of this study was to evaluate the results of the authors' modification of Salter innominate osteotomy in Perthes' disease. The operation was performed in 16 hips of 15 Perthes' patients (11 boys and 4 girls). The posterior half of the ilium was cut by a Gigli saw using a conventional method. The anterior half was osteotomized using a reciprocal saw in a direction of 45 degrees obliquely to the coronal plane and 30 degrees to 40 degrees posteroinferiorly to the sagittal plane. Stable interposition of the bone block was achieved within the osteotomy site. Bone union occurred in all cases within 4 months without displacement of the osteotomy. The mean of the center-edge angle improved from a mean 19 degrees preoperatively to 29.4 degrees postoperatively, and the average epiphyseal extrusion improved from 23% to 9.5%. The modified Salter osteotomy provided much better stability by simply changing the direction of osteotomy.