Five hundred sets of orthodontic diagnostic records of patients (age 15 years +/- 3) (228 males, 272 females) whose six maxillary anterior teeth had erupted were studied. Incidence of overlapped and crowded maxillary central incisors and magnitude of that crowding were determined, also the incidence of postorthodontic open gingival embrasures (black triangles) and width of those triangular spaces between maxillary central incisors were determined. Of the 500 patients 185 (37%) had preorthodontic crowding of maxillary central incisors. Magnitude of crowding was 1.08 mm +/- 0.94, n = 185. One hundred twenty-nine of these patients were treated. Their postorthodontic records were studied. Of the 129 cases 54 (41.9%) had a black triangular gingival embrasure space between the two maxillary central incisors postorthodontically. Width of the triangular space was 0.43 mm +/- 0.32, n = 54. One third of a similar population of orthodontic patients can be expected to have crowded central incisors. Two-fifths of those can be expected to have a postorthodontic black triangle when treated similarly.