Extensive research on forest stream water chemistry gives important information in understanding the effects of environmental changes in forest ecosystems. The chemical properties of stream water from 45 forested watersheds in university forests over Japan were investigated in June, 1998. The average pH was 7.1 (maximum 8.1, minimum 6.1). The average electric conductivity (EC) was 64 (maximum 178, minimum 19) μS/cm. The EC of stream water in Okinawa and Sado Island sites tended to be high because the effects of sea salt. Except for the island sites, EC had a positive correlation with pH, summation of cation and alkalinity (mostly HCO3-). This suggests that the water showed a high EC value and a high pH value caused by the consumption of proton (H+) in streams where carbonate weathering brings a high cation concentration. The NO3- concentration in the Kanto mountainous region sites was high compared with the concentration of other sites. In Gunma sites, the relationships between NO3- and Ca2+ concentration had a close positive correlation. It was considered that exchangeable Ca2+ in the surface soil was discharged due to the increase of H+ produced by nitrification.