Black bear (Ursus americanus) populations are most often managed based on sex and age composition of hunter-killed bears, but few studies have evaluated the method used to determine age. We assessed the accuracy and consistency of aging black bears in New Mexico using the cementum annuli technique by examining age estimates obtained for research-captured and hunter-killed bears. Age estimates were 80% accurate for 30 teeth obtained from 26 known-age bears. Age estimates were consistent with field estimates of age-class for 76% of 232 teeth obtained from captured bears when actual age was not known. Age estimates were consistent between paired teeth for 74% of 232 pairs taken from hunter-killed bears on the same day but for only 46% of 61 pairs taken from study bears during the same or different years. Errors or inconsistencies in age estimation increased with known or estimated age, certainty codes provided by the laboratory, and tooth breakage, but these 3 factors were correlated. Accuracy and consistency also were lower when teeth were removed during the den season. Evidence did not indicate any difference in accuracy and consistency between sexes. In comparisons of 2 blind samples obtained independently, estimated age composition of the harvest did not differ (P=0.92). Accuracy and consistency of the cementum annuli aging technique were relatively high for bears with known or estimated ages <5 years old; therefore, the method appeared adequate for assessing age composition of annual hunter harvests in New Mexico.