Like lung cancer, mesothelioma is difficult to diagnose early. Nevertheless disease stage is the determinant factor for outcome of treatment. Effective diagnostic examinations must be undertaken promptly. Thoracoscopy is one of the best diagnostic procedures provided that it is skillfully performed to prevent complications such as development of subcutaneous nodules along the pathway of the trocar. Several arguments have been proposed against routine screening including low incidence of the disease, poor sensitivity and specificity of screening techniques, and lack of effective therapy documented by phase III study. However there are a number of arguments in favor of screening. The high-risk population is well defined. Although no control study is currently available, promising new results have been observed in limited forms, i.e., 62% response rate at stage IA with 39% survival at 5 years in patients presenting epithelial forms without lymph node involvement treated by pleuro-pneumonectomy, chemotherapy, and radiotherapy. Screening is necessary to recruit more early-stage patients for further clinical trials to improve therapeutic techniques. Poor outcome of treatment could be due to delayed diagnosis. Early diagnosis is also needed to allow compensation of occupational disease to begin while the patient is still alive.