Depending upon the adaptations considered, Chow and Chang (2006) classifies adaptive designs into several types of adaptive designs. Among these adaptive designs, seamless adaptive designs (e.g., phase I/II or phase II/III adaptive design) are probably the most commonly employed in pharmaceutical/clinical development. In early clinical development, phase I/II adaptive designs are two-stage adaptive designs that combine a phase I study (Stage 1) and a phase II trial (Stage 2) into a single trial. In practice, phase I/II adaptive designs can be classified into four categories depending upon the study objectives and study endpoints used at different stages. In this presentation, statistical issues and regulatory concerns regarding phase I/II adaptive designs with different study objectives and/or study endpoints are discussed.