A healthy volunteer is someone in a clinical trial with no known related health problems. Normally only used in phase 1 studies, researchers need healthy volunteers to establish a healthy or optimal reference point. They use data from healthy volunteers to test new treatments or interventions, not to provide direct benefit to participants. A patient volunteer is someone in a clinical trial who has the particular condition being studied. Researchers need patient volunteers to learn if new treatments are safe and effective. Not all trial participants will receive experimental medications or treatments; sometimes, participants may receive a placebo. Researchers need to vary medications and treatments so they can compare results and learn from their differences. While a study’s treatment or findings may help patients directly, sometimes participants will receive no direct benefit. However, in many cases, study results can still serve as building blocks that are used to help people later.