The methods most often used for follow-up of ovarian cancer are physical examination, CA-125 measurement and ultrasonography or computed tomography. In the present study the role of cul-de-sac aspiration cytology as a supplementary method was evaluated. We analyzed the records of 110 stage I-IV ovarian cancer patients who had undergone cul-de-sac aspiration as a part of their follow-up schedule after the primary treatment. During the median follow-up of 5 years altogether 577 cul-de-sac aspirations were performed with a median interval of 9 months. Only in 2 cases the obtained sample was insufficient for evaluation. Twenty patients had cul-de-sac cytology > or = class III at some point during the follow-up. In 12 cases the preceding or subsequent CA-125 values taken within 3 months were < 35 U/l. In 7 cases CA-125 values increased later, but in 5 cases the tumour marker values remained within normal range during the entire follow-up. Nine out of these 12 patients had a clinical recurrence later on, but 3 patients had no evidence of the disease. Twenty-seven recurrences were detected during the follow-up. Cul-de-sac aspiration cytology was the first or the only indication of recurrence in 9 cases (33%) and is a useful supplementary method in the follow-up of ovarian cancer.