Water quality data from the upper Dunajec watershed collected by the state monitoring service in the last 25 years (1977-2003) were examined to asses the evolution of water quality indicators and evaluate the limnological status of the recently constructed Czorsztyn reservoir. The characterization of the watershed and its hydrology is followed by the presentation of physico-chemical and some biological descriptors. The discussion emphasises the temporal trends and links between various observations. It has been concluded that the deterioration of physico-chemical water quality of the upper Dunajec river observed between 1977 and 1988 has been partly reversed due to the construction of wastewater treatment plants and possibly due to the collapse of economic development in 1989.