PIP: This article, written by a resident of Thailand, argues that placebo-controlled trials of treatments to prevent maternal-fetal transmission of HIV infection are sometimes justified in settings where treatment is otherwise totally unavailable because at least half of those involved would likely benefit. However, different developing countries have different levels of resources, and efforts should be made to perform equivalency studies as an alternative to placebo-controlled trials, especially those involving zidovudine, which is a standard of care in developed countries. When placebo-controlled trials of short-course zidovudine began in Thailand in 1994, zidovudine was not being routinely offered to patients because of financial constraints and a lack of the necessary treatment infrastructure. As time passed, situations changed (in 1996 efforts began to procure zidovudine for impoverished mothers), and a trial that seemed ethical in 1994 could be considered unethical in 1997. Thus, in 1997, one placebo-controlled trial of short-term zidovudine therapy was terminated early but another, sponsored by the US Centers for Disease Control and Prevention, is slated for completion in 1998. This decision to complete the trial led to local and international controversy because the affected women were not informed about treatment options. Another unjustified and unethical study sponsored by the US Walter Reed Army Institute of Research in Lampang seeks to determine the natural history of perinatal HIV infection and only recently offered women and newborns zidovudine treatment.