This thesis has studied about the legal characteristic of injection of the trial drug, the position of the pharmaceutical firm as a contractor of the clinical trial, the possibility of compulsory performance of consistent injection of the trial drug, and the damage claim caused in the process of the clinical trial from the viewpoint of protecting the trial subject in the clinical trial. According to court's judgement in the United States, the lawsuit of the trial subject, although the trial subject had expected consistent injections, was dismissed because there was no direct contract between pharmaceutical and trial subject. However, Helsinki Declaration prescribe the medical research as follows. 'All patients who participated in the research should be able to use the best precaution, diagnosis, and treatment proved by the final outcome of the research'. The trial subject is entitled to demand only the pharmaceutical firm which developed and provided the trial drug, and the pharmaceutical firm has the obligation to supply the trial drug to the trial subject. Therefore, it would be not enough to protect the trial subject if the pharmaceutical firm which makes the trial drug is ruled out. In addition, especially, in case the trial drug has a constant effect with the aim of treatment, if the injection of the trial drug is suddenly stopped, the trial subject would not have the benefit of treatment by the trial drug. In this case, the best remedy against the damage is to urge a constant injection of the trial drug. Thus, in certain case, it is reasonable to consider that the pharmaceutical firm has the obligation to supply the trial drug to the trial subject constantly, and it is also necessary to compel it through effective means in case the pharmaceutical firm do not fulfill its obligation to supply the trial drug. However, as an essential prerequisite for the assertion mentioned above, it should be judged under the principle of good faith considering the concrete situation, that is, what roles the pharmaceutical firm has played.