Water sources and ¯ow paths contributing to stream chemistry were evaluated in four Japanese forested watersheds with steep topography (slopes 5308). Stream chemistry during periods without rainfall and during events with less than 100 mm of precipitation was similar to seepage water chemistry, but markedly dierent from that of soil water which had higher concentrations of NO À 3 and Ca 2 and lower concentrations of Na and HCO À 3 . Also, stream Cl À concentrations in a Cl À -treated watershed did not increase either during events with less than 100 mm of total rainfall or at base¯ow conditions, even three years after the Cl À treatment. These results suggest that groundwater within bedrock ®ssures of Paleozoic strata had a long residence time and was a major contributor to steam water under base¯ow conditions and even during small precipitation events (5100 mm). In contrast, for large precipitation events (4100 mm), stream chemistry became more similar to soil water chemistry, especially within the steepest watershed. Also, for large precipitation events, stream Cl À concentrations in the Cl À -treated watershed increased markedly. These results suggest that soil water was a major contributor to stream waters only during these large events.