Stream water samples were collected from headwater streams in Vermont and New Hampshire during low-flow periods in the fall and analyzed for principal dissolved constituents. Dissolved solids are qualitatively and quantitatively related to bedrock type. Streams draining watersheds underlain by plutonic bedrock are acid, mixed cation sulfate waters with little buffering capacity and very low solute content (about 16 mg/1). Streams draining metamorphic and sedimentary terrains are characterized by neutral pH, alkaline earth cations, and mixed anions or bicarbonate. Concentrations of Ca + Mg + Na + K and pH of streams draining granitic bedrock are lower than those of streams draining similar rock types in small watersheds in the Sierra Nevada and Sangre de Cristo mountains.