A midline diastema usually is part of normal dental development during the mixed dentition. However, several factors can cause a diastema that may require intervention. An enlarged labial frenum has been blamed for most persistent diastemas, but its etiologic role now is understood to represent only a small proportion of cases. Other etiologies associated with diastemas include oral habits, muscular imbalances, physical impediments, abnormal maxillary arch structure, and various dental anomalies. Effective diastema treatment requires correct diagnosis of its etiology and intervention relevant to the specific etiology. Correct diagnosis includes medical and dental histories, radiographic and clinical examinations, and possibly tooth-size evaluations. Appropriate treatment modalities have been described. Timing often is important to achieve satisfactory results. Removal of the etiologic agent usually can be initiated upon diagnosis and after sufficient development of the central incisors. Tooth movement usually is deferred until eruption of the permanent canines, but can begin early in certain cases with very large diastemas.