Clinical trial is a part of clinical research. It is a systematic experimental biomedical study. They are carried out to evaluate the effectiveness and safety of medications or medical devices or biologics. Trials are conducted to check safety and efficacy of new drug. It includes four phases as phase I, II, III, and IV. The study is carried out according to study protocol and standard operating procedures as per good clinical practices guidelines. The study protocol is developed by the researchers and approved by an independent committee called as Institutional Review Board. Protocol is a roadmap for team of healthcare professionals involved in investigation work. It should explain the significance of research trial, location, detail procedure, methods, activities, time allotment, financial estimate and any other information required. The content of protocol are title, objective, background, eligibility criteria, study methodology, risks or adverse effects, benefits, alternative treatment, data collection, statistical treatment, regulatory guidance, and other information.