To detect a primary neuroblastoma lesion and its metastases, 131I-MIBG scintigraphy was performed for a 24-year-old woman who had a high level of serum catecholamine. 131I-MIBG scintigrams showed high radioactivity in the left upper quadrant, pelvic bone, and vertebral bodies. A biopsy of the pelvic bone revealed metastasis from the neuroblastoma. After four chemotherapy courses, the accumulation of 131I-MIBG decreased after each course; however, scintigraphy performed after the last chemotherapy course showed focal mild uptake in the right sacroiliac. The presence of residual tumor in the sacroiliac was confirmed histologically. On the other hand, T1-weighted and T2-weighted MR images performed before the treatment showed low signal intensity and high signal intensity in the pelvic bone, respectively. After the fourth chemotherapy course, T2-weighted MR images showed low signal intensity in the pelvic bone; however, it was difficult to determinate whether it should improve. To assess the effect of treatment of neuroblastoma, 131I-MIBG scintigraphy was considered more useful than MRI.