This study was conducted in 1997-1998 in order to improve the quality of treatment of trauma care in Khon Kaen Regional Hospital by revision of the trauma audit filter which was set up in 1997. After the implementation of the revised audit filter by the method of participatory action research (PAR), the trauma preventable death rate was decreased to 2 per cent which was statistically different from the preventable death rate in 1994 and the pitfalls of trauma treatment and pitfalls contributing to mortality was also statistically significantly decreased when compared with the result in 1994 and 1995. The compliance of physicians in 23 items from 32 items in trauma audit filter was more than 80 per cent.