Placebo-controlled studies are a way of testing a medical therapy in which, in addition to a group of subjects that receives the treatment to be evaluated, a separate control group receives a placebo treatment which is specifically designed to have no real effect. I think Placebo Controlled Trails (PCT) is important, necessary and its ethical because it compares with the standard treatment and it give opportunity to compare the results. Advantages of PCT includes, it allows estimation of the assay sensitivity and internal validation of the study. It allows better evaluation of clinical relevance. The sample size is small and lower study costs. The disadvantage includes, has higher risks from the non-treatment, more limited generalized ability of the results to the general population.