Contamination of groundwaters in the United States by organic compounds is reviewed in terms of its occurrence, behavior, and treatment. The authors describe the behavior of organic solutes in the subsurface environment, considering the effects of sorption, dispersion, advection, and degradation. Examples of calculations are presented for simple cases of one-dimensional, one-phase flow in a saturated porous medium. Also considered are some implications of the organic contaminants' characteristics for water treatment. Chemical compounds discussed include the following: aliphatic alcohols; alkanes and alkenes; aromatic hydrocarbons; halogenated aliphatics; halogenated aromatics; phenols and substituted phenols; carboxylic acids; and nitrogenous compounds. Includes 32 references, table, figures.