INTRODUCTION: Several international organizations have published guidelines for the correct use of tumour markers in clinical practice. However, there are reports that clinicians do not adhere to these guidelines in clinical practice. The present study constitutes an audit of TM use in a major hospital in Northern Greece. Purpose of our study is to quantify the magnitude of inappropriate TM requests as well as the corresponding financial cost.METHODS: We examined retrospectively all TM requests between 10/2006 and 07/2007 in the department of biochemistry of our hospital. The tumour markers included in our study were: CA 19-9, CA 125, CA 15-3, AFP, NSE, CYFRA 21-1 and CEA.RESULTS: We found 9782 inappropriate TM orders. For five of them - namely CA 125, AFP, CA 19-9, CYFRA 21-1 and NSE - the proper requests were below 10%. There were 5.6 TM requests per patient. The total cost for inappropriate TM reached 239,748 euro, which corresponds to a monthly cost of 23,974euro.CONCLUSIONS: There is considerable inappropriateness in the utilization of TM in Greece which corresponds to significant financial cost. Various measures should be applied in order to increase the cost-effectiveness of TM use.