A randomized trial was conducted on 33 patients' 37 hips with early-stage osteonecrosis (ON). After the initial clinical evaluation including plain roentgenography aad magnetic resonance (MR) imaging, hips were randomly assigned to a core decompression group or conservative treatment group. All the patients were regularly followed by clinical evaluation, plain roentgenography and MR imaging at intervals of three months. Hip pain was relieved in nine out of ten initially symptomatic hips in the core decompression group, while pain persisted in three out of four initially painfol hips in the conservatively treated group on the second evaluation (p<0.05). At a minimum follow-up of 24 months, 14 of the 1S eore decompressed hips (78%) and 15 of the 19 nonoperated hips (79%) devel- oped collapse of the femoral head. By survival analysis, there was no significant difference in the time to collapse between the two groups (log rank test p=0.79). Core decompression may be effective in symptomatic relief, but it may not provide additional benefit in preserving femoral head as compared to the conservative management in early-stage ON of the femoral head.