PURPOSE: To review MRI in order to compare Gd-DTPA enhanced images before and after preoperative intraarterialchemotherapy for osteosarcoma. MATERIALS AND METHODS: In sixteen patients with pathologically-proven osteosarcomawho underwent intra-arterial chemotherapy, MR images were obtained before and after this treatment. The degree[grade 0(low) to IV(high)] and pattern (homogenous, inhomogenous) of changes in contrast enhancement and tumorsize were evaluated. RESULTS: Enhancement changed from Grade III to I in eight patients and from Grade III to IIin five. In three, the enhancement pattern changed from homogenous to inhomogenous; in ten, the inhomogenouspattern did not change; and in three, there was a change from thick, irregular to thin, smooth-rimmed enhancement.In all patients except one, the intraosseous tumor component was not changed. The extraosseous component becamelarger in three patients, smaller in two, and showed no size change in eleven. CONCLUSION: In osteosarcoma, MRimaging after Gd-enhancement following intra-arterial chemotherapy showed decresased enhancement, and increasedinhomogeneity and smooth rim enhancement. Neither the intra-nor extraosseous tumor component showed size changewith time.