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Few studies have been conducted on the diet of bears in the tropics. During 1998-2000, we studied the diet of Asiatic black bears (Ursus thibetanus formosanus) in Yushan National Park, Taiwan, on the Tropic of Cancer. We used 3 methods to investigate their diet: scats, feeding sign, and interviews with indigenous hunters. Most scats (n = 654) were found during autumn and early winter, when bears congregated in an area of abundant oaks and foraged mainly on acorns. In 1999, when acorns were less abundant, bears preyed more frequently on ungulates. We found fewer scats (n = 37) during summer, when bears were more dispersed and foraged on soft mast, and only 2 scats during spring, both containing mainly green vegetation. These findings were corroborated by bear feeding sign that we found, including hundreds of oak and soft mast-producing trees with broken branches, some forming a structure resembling a nest. We also found evidence of bears feeding on carrion and insects. It was more difficult to determine seasonality of diet using sign, although this technique yielded a larger list of bear foods (n = 26) than scat analysis (n = 19). However, the largest tally of bear foods (n = 70) was obtained by interviewing indigenous people who hunted in or near the park. Data generated from these interviews were less quantitative but covered a much broader area and time span and provided better information on the diversity and seasonality of the diet than that obtained from scats and sign. The 3 methods, each somewhat biased and deficient, yielded complimentary views of bear diets. Our results were consistent with other studies of Asiatic black bears in broadleaf forests; these bears were omnivorous, opportunistic, and heavily dependent on hard mast. In our study, however, bears consumed medium-sized ungulates more frequently than in other areas.