The effect of geologic differences and urban development on low-flow characteristics of streams in Fairfax County, Va., are discussed. Tables of annual minimum 7-day average flow values for various recurrence intervals are presented for 5 long-term gaging stations and for 37 selected low-flow measurement sites. Drainage-basin boundaries and 7-day 10-year low-flow values are shown on a 1:48,000-scale map of the county.