One of the most controversial subjects in orthodontics is the ideal time to begin an orthodontic treatment for various problems encountered in growing patients. In most cases, the main concern is the benefit of treatment at an early stage of mixed dentition in comparison with another treatment that would be started in the late mixed dentition stage or in permanent dentition. One reason for this controversy is that the “cost” for early treatment is only part of a two-phase protocol. The first phase usually involves 6 to 12 months of active treatment with the intention of changing the dentoskeletal relationship between the jaws and the second phase is the “finishing” process after the eruption of permanent teeth. Thus, the analysis of risks versus benefits becomes inevitable. Do benefits of early intervention justify the cost and duration of a two-phase treatment? Some “classic” orthodontic studies have tried to answer these questions and some will be described below.