Triazine herbicide residues were monitored in the rivers Adour, Danube, Garonne, Herault, Loire, Marne, Oise, Rhine, and Rhône from spring 1976 to fall 1977 to determine whether the continued use of the compounds resulted in accumulations of undesirable residues in the streams. Samples were generally collected monthly or bimonthly and analyzed for the parent compounds atrazine, simazine, terbumeton, terbuthylazine, and dealkylated metabolites GS 26571 (2-amino-4-etert-butylamino-6-methoxy-1,3,5-triazine) and G 30033 (2-amino-4-chloro-6-ethylamino-1,3,5-triazine). The compounds were extracted into dichloromethane and quantitated by gas chromatography (GC) with nitrogen-specific detection. Selected results were verified by GC with mass fragmentographic detection. Limit of detection was usually 0.4 mg/m3; 80 percent of all results were below 0.4 mg/m3, 14 percent were 0.4-1 mg/m3, 6 percent were 1-10 mg/m3, and 0.3 percent were higher than 10 mg/m3. Detectable residues were mainly atrazine from the downstream sampling sites. Residues usually peaked during June.