Serial quantitative scintigraphic studies using 99mTc-methylene diphosphonate were performed on 25 hips with Legg-Perthes' disease to evaluate changes in local blood flow of the femoral head after subtrochanteric varizational and/or derotational osteotomy. Studies were made preoperatively and were repeated postoperatively at 2, 4, 6, and 8 weeks at 3 and 6 months, at 1 year, and finally at 2 years after osteotomy. The relative vascularity of the affected femoral head at 2 weeks after osteotomy was significantly decreased as compared with the preoperative value. Thereafter, it increased steadily, reaching the preoperative level by 6 months with no further statistically significant increase at < or = 2 years. Our scintigraphic study showed that local blood flow of the femoral head does not increase significantly after subtrochanteric femoral osteotomy in Legg-Perthes' disease.