Abstract-Escherichia coli strains from gulls, chickens, humans, Canada geese, horses, deer, and swine exhibited nearly 25-fold differences in adhesion to kaolinite particles. Hydrophobicity and zeta potential were not correlated with adhesion. There were significant differences in adhesion patterns between avian strains and most mammalian strains, while there were no differences in adhesion patterns between domestic animal strains and wild strains, or between ruminant and non-ruminant mammals. Selected strains exhibited varying responses to changes in pH, sorbent type, ionic strength, and generational cell age. The results indicate that adhesion by different strains under varying environmental conditions is more variable than previously recognized and that sediment-adhered bacteria can represent a significant population. Such wide variation in adhesion behavior could affect the assessment of bacterial contamination in receiving waters, and has implications for field sampling techniques, laboratory culture conditions, and experimental design of water quality projects, including TMDL protocols.Index Terms-E. coli, fecal coliforms, water pollution, bacterial adhesion, microbial source tracking.