For the child with such crowding that the eruption of the permanent teeth is impeded then serial extraction may be the answer. If the crowding is due to narrow arches then expansion as outlined in section E may alleviate the problem. If the arches are normal in width then expansion should be cautiously considered as overexpansion may be unstable and leave the unaesthetic appearance of a very large mouth in a small face. Serial extraction is a “robbing Peter to pay Paul” strategy. Baby teeth in the anterior portion of the mouth are extracted earlier than average to allow the earlier erupting permanent teeth room to erupt and align. This transfers the crowding problem posteriorly. However, as the premolars are smaller than the baby molars there may be sufficient space if the excess space is maintained by a lower lingual holding arch (LLHA). In a serial extraction case there is a high suspicion that permanent teeth will need to be extracted eventually. However, during this transition period the jaws continue to develop so a reevaluation is performed before any permanent teeth are extracted. The payoff for a serial extraction case is that the teeth are able to erupt reasonably well aligned and future orthodontic treatment is both delayed and minimized. Failure to act early in a severely crowded case means the teeth will either become impacted and unable to erupt or they will erupt in a haphazard fashion requiring more extensive orthodontic treatment.