PURPOSE: Gonadotropin-releasing hormone(GnRH) analogues have been used as a conservative or preoperative therapy in the treatment of uterine leiomyoma. Since these drugs, which can induce a low estrogenic state, affect only undegenerative leiomyoma tissue, the aim of the present study was to differentiate degenerative leiomyoma from undegenerative one by Gd-DTPA enhanced magnetic resonance imaging(MRI). MATERIALS AND METHODS: There were 40 masses in 24 patients;all were diagnosed by surgical-pathology. With superconductive 0.5T MR circuit, T1- and T2-weighted images and Gd-DTPA Tl-weighted images were obtained. Based on a combination of signal intensities of T2-weighted and enhanced T1 weighted image on the! same tumor section all the lesions were classified to one of four rvlRI patterns. Pattern I was a heterogeneous hyperintensity on the T2-weighted images that was enhancement by Gd-DTPA. Pattern II was a high signal intensity on the T2-weighted MR images but no enhancement by Gd-DTPA. Pattern III was a low to intermediate signal intensity on the T2-weighted MR images and enhancement on the Gd-DTPA Tl-weighted images. Pattern IV was a low to intermediate signal intensity on the T2- weighted images and no enhancement by Gd-DTPA. Each of these 4 groups of MRI pattern were co- rrelated to the surgical-pathology findings. RESULTS: Pathologically, pattern I corresponded to an edematoMs leiomyoma in 3 cases and a connective tissue leiomyoma in one case. Pattern II corresponded to three red degeneration, two cystic degeneration and one infected leiomyoma. Pattern Ill corresponded to eighteen undegenerative leiomyomas, but some of them showed focal connective tissue proliferation. All of twelve cases in pattern IV corresponded to a hyaline degeneration. CONCLUSION: MRI with Gd-DTPA enhancement may differentiate undegenerative leiomyoma from degenerated one.