Scales and otoliths were collected from 227 wild brown trout (94-647 mmTL) from 11 Tennessee streams to assess the comparability and accuracy of the two structures for aging these fish. Accuracy was determined by examining scales and otoliths from known-age fish (up to age 5) from five streams. Maximum ages for scales and otoliths were 8 and 12 years, respectively. Overall, there was 74% agreement between corresponding scale and otolith ages (81%, ages 0-5; 21%, older fish). Scale age underestimated otolith age in 68% of cases where the structures did not agree (maximum, 5 years; mean, 1.6 years) and in 98% of disagreements involving age-3 and older fish. Consequently, the regression slope of scale age versus otolith age (0.72) was significantly different (P < 0.05) from the hypothetical slope of 1.00. All scale and otolith ages determined for known-age fish were accurate. Additionally, mean absolute ageing error for scales was <1 year through age 5, but usually exceeded a year afterward. Therefore, we conclude that scales are generally reliable for ageing wild brown trout up to age 5. Because growth of individual fish was highly variable (457-508 mm fish were 4-12 years old), length was an unreliable predictor of age for larger specimens.