Mesothelioma is a highly progressive tumor with a poor prognosis. In this article, the authors give a thorough introduction into and evaluation of the MESOMARK(®) in vitro test - the only blood test for the management of patients with mesothelioma approved by the US FDA. In Europe, Australia, New Zealand and Canada, the test is approved or licensed for the measurement of the soluble mesothelin, also termed as soluble mesothelin-related peptides. In the US, it is approved for the monitoring of patients with epithelioid and biphasic malignant mesothelioma.