Immunoscintigraphy of ovarian tumors by intraperitoneal administration of I131 HMFG2 monoclonal antibodies (mabs) was used in this study. The purpose was to evaluate the diagnostic potential of this non-operative imaging technique in detecting ovarian tumor nature and spread. Sixteen patients that received 500-1000 microCi of I131 labelled HMFG2 mabs were evaluated. The scans obtained were compared mainly with the macro and microscopic operative findings of the subsequent laparotomy. Immunoscintigraphy accurately scanned tumor spread in 7 out of 9 patients with known ovarian cancer. It also successfully revealed the malignant or benign nature of pelvic masses in 6 out of 7 patients examined.