The group of test animals or humans that receive a placebo or active control; in a case–control study, subjects without the disease or outcome. For most preclinical and clinical trials, the Food and Drug Administration will require that this group receive placebo (commonly referred to as the placebo control). However, some studies may have an active control that generally consists of an available (standard of care) treatment modality. An active control may, with the concurrence of the Food and Drug Administration, be used in studies where it would be considered unethical to use a placebo. A historical control is one in which a group of previously treated patients is compared to a matched set of patients receiving the new therapy. A historical control might be used in cases where the disease is consistently fatal (e.g., AIDS).