Purpose: Malignant pleural mesothelioma (MPM) is an extremely lethal neoplasm and continues to be an important health problem in communities facing occupational or environmental exposure to asbestos. One of the most significant problems in the treatment of MPM is the lack of a standardized criterion for the evaluation of response to chemotherapy. In this study, differences between the tumor volumes of International Mesothelioma Interest Group (IMIG) stages, chemotherapy response, and patient response times were investigated. Patients and methods: We used the initial tumor volume determinations from patients with MPM with the point-counting technique indicated in the Cavalieri principle of stereologic design. Results: We observed reduction in tumor-volumes from tumor treatment until posttreatment. We found that those patients with the shortest period between initial diagnosis of a tumor volume of 200 mm(3) or greater had increases in volume of greater than 50 mm(3). Conclusion: There is still no standardized evaluation of MPM responses after chemotherapy to chemotherapy using classic criteria. However, our studies on tumor volume continuer.