Appendectomy in primary and secondary staging operations for ovarian malignancy. Appendectomy was performed at primary or secondary staging operations in 100 patients with ovarian malignancies. Of 80 patients who underwent appendectomy at the time of their primary surgery, 25 (31.2%) had appendiceal metastases. Among 47 patients who were believed to have disease limited to the pelvis at the time of surgery--stage I (N = 34), II (N = 7), IIIA (N = 5), and those designated stage IIIC solely on the basis of microscopic para-aortic nodal metastasis (N = 1)--the appendix was involved with disease in only two patients (4.3%). However, among 33 patients with advanced disease--stage IIIB (N = 6), IIIC except those designated IIIC solely on the basis of microscopic paraaortic nodal metastasis (N = 19), and IV (N = 8)--the appendix was involved with disease in 23 patients (69.7%) (P less than .001). Poorly differentiated tumors and serous histologic cell types more frequently metastasized to the appendix (64, 15, 6, and 8% for grades 3, 2, and 1 and borderline histology, respectively; P less than .001; and 48, 13, and 8% for serous, endometrioid, and mucinous; P less than .001). Of 20 patients who underwent appendectomy at their secondary staging procedure, two had metastases. Metastatic disease in the appendix was microscopic in nine of 27 patients. Because the frequency of appendiceal metastasis is similar to that of other metastatic sites in stages I and II ovarian cancer, it should be removed at primary staging procedures. Appendectomy should also be performed in patients with advanced ovarian malignancies if it contributes to cytoreduction or at the time of secondary staging procedures. 