Clinical trial phases for medications and treatments

There are four different phases of a clinical trial. Each phase is represented by a roman numeral. Clinical trials are also referred to as clinical studies.

Test tubes at the National Cancer InstituteClinical trial phases are very important because they enable researchers to properly assess the safety and effectiveness of new treatments before being approved for use by the general public.

New medications must be tested in Phase I, II and III trials before they are approved. 

Find out more about clinical trial phases for medical devices.

Find out more about what happens in each phase below.

Phase I
Phase II
Phase III
Phase IV