The tumor-associated antigen 90K is thought to play an important role in cellular immune defense against malignant cells. It is therefore of interest to investigate whether circulating 90K could be used as a prognostic variable in ovarian cancer, and whether this immunostimulatory antigen is related to other parameters known to be involved in the cellular immune response. In the present retrospective study, circulating levels of antigen 90K were measured before primary surgery in 152 ovarian-cancer patients. A very close association between antigen 90K and s-IL-2R concentrations was pointed out in a stepwise logistic regression model. Univariate analysis of overall survival revealed that antigen 90K and s-IL-2R were associated with poor prognosis. In the multivariate Cox regression, however, neither antigen 90K nor s-IL-2R retained independent prognostic significance. Urinary neopterin was shown to be the only independent prognostic variable among the "immunological parameters" investigated. Additionally, residual disease after primary tumor debulking and histopathologic tumor grade were the most prominent clinico-pathologic parameters for the independent prediction of poor clinical outcome in ovarian-cancer patients.