The "in vitro" cell growth of 14 ovarian carcinomas was evaluated and related with the clinical-pathologic stage (FIGO) and grade of histologic differentiation of disease, with the patients' immunological pattern and with the relapse and survival rates. We identified 4 different patterns of "in vitro" cell growth (P1, P2, P3 and P4). Their correlation with the clinical-pathologic stages of disease as well as with the recurrence and survival rates was strong: 75% of recurrences in pattern P3 and 100% in pattern P4, while tumours with patterns P1 and P2 did not relapse. Similar results were obtained for survival, in fact 2 of the 3 patients who died from disease had cell growth pattern P4, and the other a P3. A significant correlation was found with basal natural killer cell activity of peripheral blood lymphocytes too: in patients with P1 neoplasia the basal NK cell activity was significantly higher (p < 0.05) while it was significantly lower (p < 0.05) in patients with P4 neoplasia in comparison with the others. We conclude that the "in vitro" biological behaviour of ovarian neoplasia can be regarded as prognostic factors even if patients' basal NK activity represents the most significant prognostic element, directly related to the recurrence rate (p = 0.002).