This study was carried out in Bursa Province, Turkey, between 1995 and 2006 in order to collect data on hesperiid and pierid species, their distribution, and current status. The butterflies were caught with sweep nets from 78 localities in 16 towns in Bursa Province, northwestern Turkey. Materials were pinned with their wings spread and put into a collection after drying. In all, 822 hesperiid and 956 pierid specimens were caught, including 17 and 16 species, respectively. The hesperiid Pyrgus serratulae (Rambur, 1839) and pierid Pieris manii (Mayer, 1851) are first records for the butterfly fauna of Bursa. The horizontal and vertical distribution, and current status of the hesperiid and pierid species were determined and are herein discussed in detail. © TÜBİTAK.