We have evaluated the prognostic value of tumour-associated trypsin inhibitor (TATI) in stage III or IV ovarian cancer. Tumour-associated trypsin inhibitor (TATI) and CA 125 were determined in serum samples from 66 patients taken before primary surgery. TATI was elevated (> 22 micrograms l-1) in 27 patients (41%). These had a 5 year cumulative survival of 8%, whereas survival was 45% in 39 patients with normal preoperative TATI values. By contrast, the preoperative CA 125 level did not predict survival. In multivariate analysis which included age, stage, histological grade and preoperative TATI and CA 125 levels, patients with elevated preoperative TATI levels had a 2.3-fold relative risk of death (95% confidence interval 1.23-4.20; P = 0.002) compared with patients with normal preoperative levels. This result was comparable with the predictive value of primary residual tumour size, since patients with residual tumour larger than 2 cm in diameter had a 5.2-fold relative risk of death (95% confidence interval 2.55-10.68) compared with patients with a smaller or no residual tumour. Thus, preoperative determination of serum TATI may have a place in the pretreatment evaluation of patients with advanced ovarian cancer.