Rather little is known about the changes in orthodontic treatment results exceeding a decade after treatment. The purpose of this study was to quantify changes in tooth relationships in a series of cases (n = 36) at 6 years and again at 15 years after treatment. The rate of change decreased with time, supporting the contention that most "relapse" occurs soon after treatment; continued change generally cannot be distinguished from normal aging processes that occur, regardless of whether a person had been treated orthodontically. There were minor, but statistically significant, associations between increased incisor irregularity ("relapse") and parasagittal growth of the jaws. Greater irregularity occurred when mandibular growth exceeded that of the maxilla, decreasing overjet and crowding the lower incisors within the containing arch of the maxilla. Overall, relapse tended to be less in these cases treated by a single experienced specialist that in university-based samples treated by multiple, orthodontic residents.