The second stage in a series of trials to determine the safety and efficacy of a drug before it reaches the public. At this stage, drugs are evaluated for a particular indication or indications in patients with the disease or condition under study and to determine the common short-term side effects and risks. The number of participants in these trials can be between 20 and 300.

See also:
Phase I trials
Phase III trials
Phase IV trials
Clinical trial
Clinical trial enrolment
Pre-clinical trials