Those who would promote policies that restrict commonly recognized rights of selected categories of persons have the responsibility of demonstrating that the threat is real and that the restrictive action will be effective. However, the currently available evidence does not justify the assumption of a causal connection between international population movements and the spread of AIDS. Several nations currently have policies that require testing of foreign students, foreign workers, nationals returning from abroad, foreign diplomats, and all or most foreign immigrants and persons desiring long-term residence. Nevertheless, a World Health Organization consultant group has concluded that mandatory screening of international travelers is unlikely to reduce the spread of HIV to and within countries. This would be true even for a nation with no HIV infection, assuming that nationals traveling abroad would have to be re-admitted even if they tested positive. Data tables and 5 references.