The interaction between pedospheric and atmospheric sulfur nutrition was studied in seedlings of Norway spruce. Spruce was grown on a 25% Hoagland nutrient solution containing 35S-sulfate and simultaneously exposed to 250 nl l −1 atmospheric SO 2 or H 2S. A 6-day exposure to SO 2 and H 2S resulted in a substantial increase in the total sulfur concentration of the needles. This increase could be ascribed to increased needle concentrations of sulfate, water-soluble non-protein thiols and organic sulfur. SO 2 and H 2S exposure resulted in slight but significant increases in the concentration of sulfur compounds in roots. In all sulfur fractions, except sulfate, there was a substantial decrease in the level of 35S in needle and root sulfur fractions upon SO 2 and H 2S exposure, demonstrating that spruce was able to switch from pedospheric sulfate to atmospheric sulfur as a source for growth. In needles, the amount of 35S decreased in total organic S and glutathione fraction, whereas it increased in sulfate. This supports continued import of S taken up by the roots into the needles in spite of a decreased channeling of 35S into synthesis in needles. A greater part of total sulfate increase was due to unlabeled S, which points towards metabolic oxidation of H 2S and SO 2 to sulfate. Increased concentrations of S compounds (including sulfate) in roots were mainly due to unlabeled S, indicating an import of sulfur from the foliage. The significance of glutathione in the translocation of reduced sulfur from the needles to the roots is discussed.