Chromogranin A is a main, nonspecific neuroendocrine tumor marker (NET). It's estimation was applied for diagnostic purposes and for monitoring the treatment of NET. Currently few commercial assays are available allowing measurement of CgA concentration in serum or plasma. These methods have various sensitivity and specificity and differ in many analitycal parameters. Numerous factors and pathologies may influence the outcome of the CgA measurement. Therefore, a review article on this matter may be useful for clinical and laboratory practice.