The Gynecologic Oncology Group (GOG) experience with second-look laparotomy in malignant ovarian germ cell tumors is reviewed. All patients in this study were enrolled prospectively on one of three protocols that employed relatively brief cisplatin-based chemotherapy after initial surgical staging and cyto-reduction. Forty-five surgical procedures were done in patients who received three courses of cisplatin-based adjuvant therapy after complete tumor resection. Findings were no tumor or mature teratoma in 43; 2 patients had immature teratomas. One of the latter patients received further chemotherapy and one did not. Both of these patients and 44 of the total are disease free. Seventy-two patients were treated with similar chemotherapy for advanced incompletely resected tumor. Forty-eight of these patients did not have teratoma elements in their primary tumor. At surgery, 45 patients had no tumor and 3 had persistent endodermal sinus tumor or embryonal carcinoma. All three of the latter patients are dead despite further treatment. Twenty-four patients had teratoma elements in their primary tumor. Of these patients, 16 had mature teratoma at second-look, which in 7 was bulky or progressive. Fourteen of the total 16 and 6 of the 7 with bulky residual tumor remain disease free after surgical resection. Second-look laparotomy is not necessary in patients completely resected initially or in those patients with advanced tumor that does not contain teratoma. However, enough patients with incompletely resected tumor which initially contains elements of teratoma benefit from the procedure to warrant its general use.