The only role where the CA 125 test has proven utility is: (i) for monitoring ovarian cancer (OC); and (ii) for a preoperative test in patients with an ovarian mass. The aim of our study was to assess the clinical indications for CA 125 determinations in order to estimate the appropriateness of CA 125 use. During the period of 1 August 1993 through 31 December 1995 all CA 125 assays performed at the laboratory of the Institut Central des Hôpitaux Valaisans (ICHV) and the data of the patients receiving these tests were audited in order to identify the clinical indication for the test. We have considered as 'correct indication' a CA 125 test performed: (i) during follow-up monitoring of patients having an OC and; (ii) as a preoperative test of a suspect ovarian mass. 462 patients have received a total of 1057 CA 125 assays. 84 (18%) patients have received 537 (51%) tests for monitoring OC and 68 (15%) patients, 68 tests (6%) as a preoperative evaluation for an ovarian mass. 310/462 (67%) other patients have received 452/1057 (43%) CA 125 tests for screening purposes in various clinical situations. Therefore, only 33% (152/462) patients including 57% (605/1057) of tests, had CA 125 assessments done for the correct indication. The current pattern of practice shows that a great number of CA 125 requests were inappropriate. Educational actions aimed at laboratory users concerning the optimal use of CA 125 should be considered in order to develop a more rational approach.