The U.S. Geological Survey has responsibility for investigating the Nation's water resources for source, availability, quantity, and quality. This paper describes the Geological Survey's research on organic substances in water and fluvial sediments. Results and ongoing studies are examined. Typical research includes: Separation, concentration, and chromatographic identification of volatile acids; free-flow electrophoresis fractionation of natural organic materials; identification of chlorinated insecticides in suspended sediments and bottom materials; fate of organics following underground disposal; determination of humic and fulvic acid stability constants and characterizations; identification of low-molecular weight chloroorganic constituents in water; PCB (polychlorinated biphenyl compound) distribution in aquatic environments; dissolved organic carbon in ground water; and improvement in separation and concentration schemes prior to analyses.