PURPOSE: To investigate changes in the ovary revealed by MR imaging before and after radiotherapy in premenopausal patients with cervical carcinoma. MATERIALS AND METHODS: Thirty-three premenopausal patients with cervical carcinoma underwent radiation therapy at an average dosage of 11,279 (external: 5,352; internal: 5,927) cGy. Before and after this therapy, all underwent pelvic MR imaging using a 1.5T MR scanner (GE Medical Systems, Milwaukee, U.S.A.). The average interval of follow-up MR imaging was 7.2 months, and axial T1-weighted and axial and sagittal T2-weighted MR images were obtained. The presence, size number of follicles, and differentiation of the zonal anatomy of the ovary were determined by two radiologists, who reached a consensus. RESULTS: After radiation therapy, all patients ceased menstruation. For ovaries, the detection rates before and after radiation therapy were 94% (62/66) and 39% (26/66) (p<0.05), respectively, and average ovary size was 2.6x1.9x2.2 cm before and 1.7x1.3x1.4 cm after therapy (p<0.05). The average number of ovarian follicles before and after therapy was 5.1 and 3.1, respectively (p<0.05). T2-weighted imaging, demonstrated differentiation of zonal anatomy in 74% of cases (46/62) before radiotheraphy, and 15% (4/26) after (p<0.05). CONCLUSION: Our study has shown that after radiation therapy in premenopausal patients with cervical cancer, detection rates, average size, and the number of ovaries decreased, findings which are similar to those for normal postmenopausal ovary. MR imaging can reveal structural change in ovaries.