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What is a Clinical Trial?

Lab technician mixing chemicals

A potential new treatment

Clinical trials are research studies that include human participants to test possible new medical treatments before they can be federally approved for use in the general public. The research aims to prevent, treat, control or diagnose a disease or condition, but it must be tested to determine its safety, side effects and effectiveness.

The medical treatments that are being administered to patients today started out in clinical trials. Each treatment being tested has the potential to be tomorrow's standard of care. The research process for a new treatment from the lab to the market can take years and even then, only a small percentage are ever approved as a standard treatment.

A promising new drug or treatment developed in the laboratory must be thoroughly tested, therefore it must undergo several phases before being approved:

  • Phase 0: Determine how a drug is absorbed, distributed and metabolized within the body to determine its promise for future testing.
  • Phase I: A drug is tested in a small group of people (20-80) to determine safety, dosage and side effects.
  • Phase II: The drug is given to a larger group (100-300) for further safety evaluations and effectiveness.
  • Phase III: The size of the study group is significantly expanded (1,000-3,000) to confirm drug effectiveness among a more diverse population. The drug is compared to how well it works versus standard treatments.
  • Phase IV: After the drug is approved for consumer use, these trials by the drug manufacturer determine more information about the treatment's effectiveness, in comparison to other drugs.

NEXT SECTION: How do I know if I can participate in a clinical trial?

Last modified: Jul 26, 2018
Video Links

• National Cancer Institute video shows how to search for clinical trials.

• The National Institutes of Health offers several videos on understanding clinical trials.

How to Join a Clinical Trial

Would you like to talk to someone about participating in research at the Clinical Research Center?

For cancer trials, call


For other trials, call