The pattern of lymphatic spread was evaluated in 81 previously untreated ovarian cancer patients (Stage I, 35; Stage II, 2; Stage III, 44) undergoing systematic aortic and pelvic lymphadenectomy. Positive nodes were found in 14% Stage I and 68% Stage III patients. Either pre- and paraaortic, or pre- and paracaval nodes were the only aortic node metastasis in 14% of patients. Common iliac nodes were the sole metastasis in pelvic area in 11%, external iliac in 14%, and obturator in 6% of patients. Therefore, the above node groups, which overall were the most frequently involved, may be considered those primarily invaded by the tumor. When data were analyzed according to stage, aortic nodes were the site of metastasis in 6% Stage I and 14% Stage III patients and pelvic nodes in 8% Stage I and 11% Stage III patients. Both aortic and pelvic areas were positive in 43% Stage III patients. The median number of positive nodes/patient was 2 (range, 1-3) and 4 (range 2-46) in Stages I and III, respectively. Lymphatic spread was ipsilateral to the tumor in all Stage I and in 40% Stage III patients. In Stage III metastases were also observed in intercavoaortic, retrocaval, retroaortic, internal iliac, and presacral nodes. In apparent Stage I, lymphatic metastasis seemed to be limited to one ipsilateral group, and the removal of the primary nodes ipsilateral to the tumor may be considered an adequate procedure. In Stage III, the presence of metastasis beyond the primary nodes and the frequent bilateral involvement suggest that all lymphatic tissue surround the aorta, the cava, and the pelvic vessels should be removed if a cytoreductive intent is pursued.