Ethics, law, and politics converge in three areas relating to AIDS: discrimination against HIV-infected persons, confidentiality of diagnosis, and exercise of the coercive powers of the State. An analysis is made of these areas, with particular emphasis on experience in the United States. Discrimination against HIV-infected persons is objectionable for moral reasons and may be counterproductive to public health. Irrational beliefs regarding the ease of contracting HIV infection are not uncommon and lead to the exclusion of infected persons from workplaces and schools. Such discrimination could lead to resistance to voluntary testing and to all contact with health care services, and could, in the final analysis, produce harmful effects. Confidentiality with regard to medical diagnosis of AIDS was considered very important in the United States during the first years of the epidemic, but health authorities subsequently began to require notification of the names of infected persons for inclusion in a confidential registry. In September 1985 the State of Colorado made it compulsory to notify the health authorities of positive results of HIV antibodies tests, and 18 states have followed suit. Notification of third parties poses complex problems. Generally speaking, it is considered that health personnel have the right, but not the obligation, to inform those who are exposed to risk. The notion of coercion with regard to AIDS has been favored by disapproval of behavior linked to transmission of the infection. Isolation policies that have been put into effect in certain countries have been vigorously debated. In several nations certain behavior entailing risk of transmitting the infection has been penalized.