Volatile organic compound (VOC) concentrations in surface waters from the Brazos River and across the river/seawater mixing zone ranged from 30 to 18,200 ng/L. Molecular level compositions were highly variable. Normal alkane, alkyl aromatic, and halogenated compounds were the dominant VOC detected. Individual compound concentrations were generally less than 10 ng/L, although occasional levels as great as 1000 ng/L were encountered (usually near point sources). The VOC detected had an anthropogenic source. Once introduced to the water via runoff and direct discharge, the main mechanism controlling the VOC concentrations was rapid (within hours) loss to the atmosphere. Sediment resuspension of VOC may have been observed across the river/sediment mixing zone. © 1988.