Serial blood samples have been obtained from 12 patients with ovarian cancer who were treated by surgery and, generally, chemotherapy or radiotherapy. Some achieved clinical remission, but the majority relapsed after variable time interval. Three potential tumour markers (Circulating Immune Complexes, Pregnancy Associated beta 1-Macroglobulin and Galactosyltransferase) have been studied longitudinally in serum for clinical correlation, predictive value, and biochemical 'lead time' to clinically detectable progression. None of the 3 offered any signal advantage over the others, and each showed an inconsistent relationship to observed disease status, with high levels indicating a poor outlook and the converse not true. Thus, since the 'lead time' is short, and reliability low, none of the compounds can be strongly commended as individual markers for ovarian cancer.