The etiology of cancer is multifactorial. Malignant tumors caused by factors occurring in the work environment, classified as carcinogenic in humans, can be recognized as an occupational disease. Analysis of epidemiological data indicates a significant underestimation of occupational cancer, mainly due to long latency period of these diseases. This publication provides guidance to certify occupational etiology of malignant tumors, based on the reviews of existing legislation and medical literature, as well as on the experience of their authors. The publication presents the epidemiology of cancers, including occupational cancers, risk factors, occupational carcinogens and presents the principles of occupational cancer certification. Med Pr 2018;69(1):93–108