Early phase trials differ from pivotal trials because they have different objectives and, often, fewer resources as well. At the same time, the information generated in early phases (effect size, feasibility, dose-response, sensitivity/specificity, etc.) must be sufficient for planning an optimal pivotal trial. In this presentation we will survey issues associated with early and late phase trials such: “exploratory” vs. “confirmatory,” endpoints and time at which measured, “operational bias” and sample size. We will then show how to optimally design your early phase trial to provide information that will maximize your chance for pivotal success.