The tabanid fly fauna and their seasonal prevalence were surveyed with a mosquito-net and NZI traps baited with 2kg of dry ice at 2 municipal pastures in Shibetsu and Rumoi, of north-western Hokkaido, Japan from June to September in 2005 and 2006. A total of 467 flies of 10 species in 5 genera were captured at Shibetsu, and 956 flies of 13 species in 6 genera at Rumoi. At Shibetsu, Tabanus nipponicus was the dominant species followed by Hybomitra distinguenda and T. trigeminus. Tabanus nipponicus was also the dominant species at Rumoi, followed by T. rufidens and T. chrysurus. Hirosia sapporoensis was abundantly captured in Rumoi but not collected in Shibetsu. The fly numbers showed a peak in late July at Shibetsu. In Rumoi, 2 peaks were observed in late July and late August probably due to the effects of rain fall during the collection day in early August.