In oncology, dose-finding studies are largely performed only in Phase 1 clinical trials, and the maximum tolerated dose (MTD), a dose initially developed for systemic chemotherapies, is by default selected for the Phase 3 confirmatory trial. With the advent of anti-cancer therapies such as molecularly targeted agents and immunotherapies, a paradigm shift is underway from the use of conventional MTD approaches to improved dose selection strategies for oncology programs. In response to this new challenge, 2-in-1 adaptive designs were proposed, aiming to optimize dose selection while still ensuring swift delivery of life-changing new therapies to patients as quickly as possible. In addition to oncology, 2-in-1 designs with dose selection can also be applied to other therapeutic areas when appropriate. The 2-in-1 designs start the trial as a Phase 2 trial with randomized evaluation of multiple doses and select dose(s) to expand to a Phase 3 trial if expected efficacy is observed at an interim evaluation. Different variations of the 2-in-1 designs have been proposed, each incorporating distinct strategies of dose selection and testing. In this chapter, we reviewed different 2-in-1 designs with dose selection and conducted simulation studies to assess and compare the operating characteristics of such designs. Practical considerations related to the design and implementation of the 2-in-1 designs were also discussed.