In the United States, the Food and Drug Administration (FDA) requires several phases of testing before a drug can be FDA approved for the treatment of a particular condition. In Phase I studies, the drug must prove tolerable and safe in a small sample of healthy volunteers (twenty to eighty subjects). In Phase II studies, the drug must prove tolerable and safe in a larger sample of patients (100 to 300 subjects) with some evidence of efficacy. In Phase II, the drug must show efficacy, tolerability, and safety in a larger sample of patients (1,000 to 3,000 subjects).