Viruses and bacteria are the cause of a large number of different human diseases. It is believed that some of them may even contribute to the development of cancer. The present work is dedicated to the identification of mycoplasmas in patients with breast cancer. Mycoplasmas may participate in the development of several human diseases including chronic fatigue syndrome, acquired immunodeficiency syndrome, atypical pneumonia, etc. Moreover, there is a reason to believe that mycoplasma can participate in the development of cancer, leukemia and lymphoma. DNA samples from blood, saliva and tumor tissues of the Oncology Institute of Moldova patients diagnosed with breast cancer were analyzed. Mycoplasma testing was performed using nested PCR method. For Mycoplasma spp. detection, we used primers from the region of the 16S-23S RNA genes. The identification of Mycoplasma faucium, Mycoplasma salivarium and Mycoplasma orale was performed by nested PCR with primers for RNA polymerase beta subunit gene corresponding to mycoplasma. M.faucium and M.salivarius was found in saliva at about 100%, and M.orale at a frequency of about 50%. Only M.faucium was found with the frequency of about 60% in the tissue of the patients. Moreover, a fairly high rate of detection of mycoplasma is observed both in the cases when primers for RNA polymerase gene and primers for 16S-23S RNA were used. We found M.faucium in tumor tissues of patients diagnosed with breast cancer. It is known that mycoplasmas are able to stimulate the synthesis of certain cytokines, which act as mitogenes on the cell. We assume that M.faucium can stimulate the mitogenes synthesis in breast tissues (e.g., cytokines) which, in turn, stimulate cell division and thus participate in the initiation of breast cancer.