Introduction. Nowadays, cancer is the second leading cause of death globally and it is estimated that in next years, the number of new cases is going to rise. So, this disease has a great impact on physical, emotional and financial aspects of everyone’s life and it would be better to prevent it consequences that to bear them. Aim of the study. Carcinogenesis may result from the action of different factors such as chemical, physical, biologic and/or genetic injuries that affect human cells. In order to discover new methods of treatment, it is important to know how cancer appears, what factors may accelerate this process and how malignant cells start to spread throughout the body. Materials and methods. This review represents a synthesis of current information about carcinogenesis from online biomedical literature such as - journals and books, including more than 30 references. Results. Cancer is a general term that describes a large variety of diseases. The common characteristic of this process is the transformation of a normal cell into a cancerous one. Oncogenesis is divided into three stages: initiation – when one or more stable cells are exposed to the action of a carcinogen factor; promotion – where the initiated cells start to expand by from the primary tumor and to gain the property that allows them to invade other organs and tissues, forming metastatic growths. In the end of this process, a cancerous cell must be able to multiply under conditions that for a normal cell would not be possible. Angiogenesis and lymphangiogenesis have an important role for tumor growth and development of metastasis. Different types of cancer genes like oncogenes and tumor suppressor genes are also involved in cancer development. If these genes gain mutations, it may lead to abnormal cell proliferation and suppression of apoptosis. Several internal factors like age, genetic predisposition, sex, along with other extrinsic factors such as chemical substances, radiations, food, tobacco have an indisputable role in determining cancer risk. Conclusions. All the accumulated knowledge about the development and progression of cancer must be used in order to develop more precise diagnostics and more effective and less toxic cancer therapies. The goal of contemporary medicine should be oriented to offer to every patient that suffers from cancer a therapeutic regimen that is tailored to his individual disease in an optimal way.