The rapid development of molecular biology techniques as well as recent progress in the understanding of genetic and molecular basis of human diseases have had enormous impact in the practice of clinical pathology. Since new diagnostic (molecular) tools are now available, the concept of Molecular Pathology is emerging. Molecular Pathology is defined by the use of molecular biology techniques and the type of specimens that are involved in its practice, basically ARN and ADN, extracted from cytological and tissue specimens. Although most methods used in molecular pathology and their applications are still under investigation and clinical validation they have great potential in several areas of pathological diagnosis, particularly on infectious and neoplastic diseases. Introduction of these techniques in pathology laboratories in our country should significantly enhance the diagnostic and research skills in the field.