The quality of water in the Ping River at 4 locations was analysed every month from January to December 1996. According to the chemical and biological factors measured, only dissolved oxygen (DO), biochemical oxygen demand (BOD), ammonia-nitrogen (NH3-N) and coliform bacteria affected the classification of the water resourecs quality. This confermed to the criteria of the National Environment Committee Announcement No.8 (B.E. 2537). The water quality of the Ping River at Pa Dad(location 1) was better than that at Ban Sri Donchai School(location 2). Ban Wang Singcome(location 3) and Mae Ping Weir(location 4) were in the category 2-4 i.e. of medium quality. The water quality at location 2,3 and 4 was in the category 4-5 i.e. poor. Location 2 was the poorest due to pollution from the adjacent, while water discharged from Mae Kha Canal affected the water quality at location 3 and 4. The overall chemical and biological quality assessment in 1996 indicated that the water of the Ping River is fit for industrial and transportation purpose only.