The last two decades have witnessed intense debate over the ethical legitimacy of placebo controlled trials (PCTs). Most of the arguments for and against the use of PCTs turn on one of the following issues: (1) the compatibility of the obligations of clinicians and researchers with PCTs, (2) the scientific merit of PCTs, and (3) the influence of patients' and subjects' perceptions, ability to consent, expectations, and rights on the permissibility of PCTs. I introduce each of these categories and assess the principal arguments in each group. I argue that, although some of the arguments against PCTs have limitations, they do inform the debate in significant ways by pointing to important constraints on PCTs. Those concerning patients' and subjects' perceptions, capacity to consent, expectations, and rights are particularly instructive. They do not, for the most part, sustain an absolute prohibition of PCTs, but they do suggest types of PCTs that are inappropriate and they indicate issues that must be addressed when PCTs are conducted. I argue that we should look to the reasonableness and permissibility of informed refusals of care (1) to evaluate the extent to which a trial is a legitimate PCT (e.g., cases in which clinicians would be highly suspect of accepting informed refusals may be more problematic than PCTs in situations in which clinicians would be comfortable accepting informed refusals); (2) to determine which potential subjects should be considered eligible to enroll in a PCT (e.g., those who would not be permitted to refuse treatment generally might not be eligible to enroll in a PCT); and (3) to inform the language that should be used in describing the study as part of the informed consent process (e.g., prospective subjects should be asked if they are willing to forgo treatment and not enroll in the trial).