Generally, physicians have a legal and ethical obligation of keeping confidentiality regarding their communications with patients. So, the most complicated ethical and legal questions arise when the HIV-infected person deliberately avoids to report to the interested individuals about the possibility of HIV transmission. The decisive factor, which emphasizes the need of such a discussion about confidentiality in HIV cases, is the character of the HIV: HIV is incurable, causes the danger of fatal outcome, discrimination etc. The aim of the paper is to explore the limits of confidentiality, as there is a duty to warn the third party about the danger of HIV transmission in that case on the part of the physician, even when the HIV-infected individual categorically refuses doing so. The paper analyses some specificities of confidentiality keeping in HIV pandemia, the responsibilities of a physician concerning the third party and his duty to warn him/her. Special attention is paid to those cases, when the fact of HIV infection has to be reported upon the patient's death or when the disclosure of the confidential information is connected with the possibility to start the post-exposure prophylactics. The paper presumes that confidentiality is not an absolute value, when there exists a real danger to the third party (e.g. a spouse, a care-taking relative, a victim).