Analyses of St. Clair River bottom water samples along 20 transects, each comprising three stations at 10 m, 25 m, and 100 m offshore, show inputs of benzene and toluene in the near-shore zone along the highly industrialized area below Sarnia, Ontario. Minimum loadings of 18 kg multiplied by (times) day** minus **1 benzene and 15 kg multiplied by (times) day** minus **1 toluene are calculated from the observed concentrations. In addition, a number of other volatile hydrocarbons were present in most samples and were tentatively identified as five to six carbon atom containing branched alkanes.