The result of thirty-six core decompression procedures in 31 patients (36 hips) with early staged osteonecrosis of the femoral head were retrospectively analyzed to ascertain the effectiveness of the procedure. Selective angiography of the medial femoral circumplex artery was performed all cases of core decompression. Collateral circulation was noted in 27 patients. Interruption of superior retinacular artery appeared only in fifteen hips without correlation with radiographic staging. The patients were for 1.1 year to 6 years (average, 2 yrs and 6 mon). The good results were obtained in 75% of Ficat's stage I and in 67.9% of stage II hips, clinically (Ficat's criteria for resuts). On radiographic results, it was good in 62.5% of Stage I hips and 64.3% of Stage II hips. We concluded that core decompression procedure is effective in the treatment of early stage (Ficat stage I or II ) of idiopathic osteonecrosis of femoral head.