The water quality classification system in Finland consists of three different sub-systems: a quality-based classification of watercourses for recreational purposes, a raw water (for domestic use) classification and a quality classification of watercourses for fishing. As a combination of these three sub-systems a general water quality classification has been widely used since 1988. However, there is a need to improve this system to be more sensitive in classification e.g. in the occurrence of harmful substances, especially organic chlorocompounds originating from pulp bleaching, and the early stages of eutrophication in very oligotrophic lakes. Also the quality classification of small rivers, very typical for Finland, needs more data about the biocoenosis, the living part of the river. Some ideas to improve the classification system in these respects are presented.