It was the aim of this study to evaluate the clinical significance of the monoclonal test system CA 125 in comparison to 7 conventional laboratory procedures (TPA, PHI, CEA, LDH, GGT, AP, ESR) as tumour marker in ovarian cancer. Serum samples from 327 patients with histologically proven cancer of the ovary were analysed. Marker results were correlated to tumour activity as defined by the criteria of the UICC. Furthermore, in 175/327 patients who were clinically symptom-free after primary therapy, marker courses were analysed with regard to the development of recurrence. Positive rates and median values of CA 125, TPA, PHI and ESR showed significant increases with progression of the disease, whereas correlation was less clear-cut with CEA, LDH, GGT and AP. In clinically tumour-free patients without evidence of recurrence during the further course, intermittent increases of PHI, ESR and especially TPA were found in 19-47%. However, such "false positive" marker courses were not seen with CA 125. Those patients who developed recurrent disease exhibited increasing CA 125 titres in 68%. The incidence of such "true positive" markers courses was less frequent with PHI, ESR and TPA. Our results indicate that CA 125 and--with limitations--TPA, PHI and ESR may be used in ovarian cancer control. When monitoring tumour-free patients, CA 125 exhibited the highest specificity and sensitivity. Using 65 U/ml as cut-off, a positive CA 125 titre indicates recurrent disease with great certainty. When employing PHI, ESR and especially TPA, however, the possibility of "false positive" increases has to be taken into account.(ABSTRACT TRUNCATED AT 250 WORDS)