Superiority clinical trials are often conducted to establish superior treatment effect of an experimental treatment compared to the control treatment. Noninferiority clinical trials are frequently designed to establish that the treatment effect of an experimental treatment is not much worse than that of an active control treatment, while the experimental treatment may offer other advantages such as reduced toxicity and/or cost. This article provides a brief introduction to the design and analysis of superiority and noninferiority clinical trials. The main issues discussed include, randomization and blinding during treatment allocation, prespecification of the noninferiority margin, the requirement of effective active control in noninferiority trials, risk of type I and type II errors, sample size and power analysis, and assessment and comparison of treatment effects between different treatment groups.