Tumour markers are substances related to the presence or progress of a tumour. An ideal tumour marker is (1) detectable only when malignancy is present, (2) specific for the type and site of malignancy, (3) correlates with the amount of malignant tissue present and (4) responds rapidly to a change in tumour size. At present, no tumour marker fulfills all of the above criteria. The first part of the review discusses the clinical usefulness of the commonly requested serum tumour markers, namely, prostate-specific antigen (PSA), CA 19-9, carcinoembryonic antigen (CEA), CA 125, CA 15-3, human chorionic gonadotrophin (hCG) and alpha-foetoprotein (AFP). It is hoped that this review article will decrease the abuse and misuse of these commonly requested serum tumour markers. The second part of the review discusses the clinical usefulness of catecholamines and their metabolites, calcitonin, thyroglobulin, parathyroid hormone, prolactin, adrenocorticotrophic hormone, oestrogen and progesterone receptors, p53, HER-2/c-erbB2, BRCA1 and BRCA2.