Table 2.

Criteria Used to Classify Study Phase^a

Study phase	Description
I	Study carried out to assess a new approach in a small sample for the first time to evaluate its safety, determine a safe dosage range, and identify side effects
II	Approach is given to a larger sample to see if it is effective, further evaluate safety, and determine optimal dose
III	Approach is to a large sample to confirm effectiveness, monitor side effects, make comparisons to commonly used treatments, and collect information that will allow the approach to be used safely
IV	Studies are done after the drug or treatment has been marketed to gather information on the drug's effect in various populations and any side effects associated with long-term use

^aI, II, II, IV, from clinicaltrial.org.