Interleukin-1 (IL-1) is a multifunctional cytokine playing a central role in the immune response and displaying direct cytotoxic activity in vitro. Serum IL-1 alpha and beta levels were measured by enzyme linked immunosorbent assay (ELISA) in 75 ovarian cancer patients, 30 patients with benign ovarian cysts and 50 healthy controls. Both serum IL-1 alpha and IL-1 beta levels were more often elevated in ovarian cancer patients compared with healthy controls (chi-square test, P < 0.001 and P < 0.001, respectively). Mean serum IL-1 alpha and beta levels decreased significantly after surgical intervention (paired t-test, P = 0.0001 and P = 0.0002, respectively). No correlation with histopathological parameters and overall and disease-free survival was found. These preliminary results indicate that serum levels of IL-1 alpha and beta represent a host defence reaction rather than an autonomous tumour cell production.