Comparative effectiveness studies, referred to here as “usual-care” trials, seek to compare current medical practices for the same medical condition. Such studies are presumed to be safe and involve only minimal risks. However, that presumption may be flawed if the trial design contains “unusual” care, resulting in potential risks to subjects and inaccurately informed consent. Three case studies described here did not rely on clinical evidence to ascertain contemporaneous practice. As a result, the investigators drew inaccurate conclusions, misinformed research participants, and subjects’ safety was compromised. Before approving usual-care protocols, IRBs and scientific review committees should evaluate the quality and completeness of information documenting usual-care practices. Guidance from governmental oversight agencies regarding evidence-based documentation of current clinical practice could prevent similar occurrences in future usual-care trials. Accurate information is necessary to ensure that trials comply with government regulations that require minimizing research risks to subjects and accurate informed consent documents.