Tumour markers are the molecules produced or induced by the tumour cell and they reflect the growth of the tumour cell. Tumour markers are not cancer-specific, as the majority of them are also synthesised and released by normal cells, which is how their reference ranges are established. The specificity of tumour markers is connected with their concentration and with the detected dynamics of their concentration. Various benign pathologies which affect the tissues producing tumour markers can also cause an increase in the serum levels of these tumour markers, leading to false positive results. The majority of the tumour markers lack the sensitivity and specificity needed for use in early detection of cancer. Still, tumour markers can be useful for diagnosis of tumour recurrence and for monitoring treatment. The physician should always consider the patient`s clinical status and presence of concomitant diseases when ordering and interpreting the results of tumour markers.