Malignant pleural mesothelioma (MPM) is a serious issue worldwide because of its increasing incidence and poor prognosis despite real recent improvements in the disease management. Most of the patients are diagnosed late in the course of the disease when radical treatment is no more an option. Therefore an earlier diagnosis of MPM is needed to significantly increase the survival of patients. Some soluble markers, including soluble mesothelin and osteopontin, have been previously proposed for MPM diagnosis but none has been validated yet. Soluble mesothelin, assessed in blood and in pleural effusion, seems to be the most promising candidate. However, even if it has a good diagnostic and prognostic value, it is quite specific for the epithelioid subtype, the most frequent one of mesothelioma, thus limiting its usefulness in practice. Despite sometimes a good sensitivity, other potential markers as osteopontin are of little interest for MPM diagnosis because of a low specificity. In conclusion, the present data do not justify the use of biology for MPM diagnosis in routine yet but rather suggest a need for a continuing evaluation of soluble mesothelin in clinical studies and the search for other potential tumor markers.