The seasonal distribution of adult Tabanidae was studied in 2 Quebec localities for 2 years: Trois-Rivieres, located in the temperate zone (46o20'N) and the Lake Delorme area, in the high-subarctic (55o00'N). Of the 43 species collected in southern Quebec, Chrysops aestuans was the dominant species, followed by Hybomitra pechumani, H. lasiophthalma, C. frigidus and H. zonalis. The flight period began in mid-May with the greatest abundance from mid-June to mid-July. Five phenological groups were distinguished by first appearance of the species and their respective abundance peaks. In the Lake Delorme area, 20 species were identified of which 12 were also present in the southernmost area. Hybomitra arpadi was the dominant species followed by C. furcatus, C. excitans and H. zonalis. The flight period began on July 8 with the most activity during the third week of July.