Technical Abstract: Six 1-ha paddocks of tall fescue (Festuca arundinacea) grazed by Gelbvieh x Angus heifers from 1 March to 21 June were used to determine the prevalence of E. coli O157:H7 and Salmonella in water tanks, and the surface water and surface soil surrounding water tanks in tall fescue paddocks grazed by cattle. Paddocks included two each of Kentucky 31 endophyte-infected tall fescue (E+), Jesup tall fescue with the AR542 endophyte strain (MaxQ), and HiMag tall fescue with strain 4 (HiMag4). Samples were collected weekly (6 June to 5 July) from water tanks (n = 30), surface ground water (n = 18) and surface soil (n = 30) surrounding the water tanks in each paddock commencing 3 weeks prior to termination of grazing until 2 weeks after cattle removal. Consumption of E+ tall fescue did not influence (p > 0.10) the prevalence of E. coli O157:H7 or Salmonella in or around water tanks. Prevalence of E. coli O157:H7 tended (p = 0.07) to be increased in the surface ground water and surface soil surrounding water tanks when areas around the water tank were muddy and cattle were present. Neither E. coli O157:H7 or Salmonella were detected in water tanks. Percentage of surface ground water samples positive for E. coli O157:H7 was 27.8% and 5.6% for Salmonella when cattle were present. Escherichia coli O157:H7 (6.7%) and Salmonella (10%) were detected in the surface soil surrounding the water tanks when areas around the water tank were muddy and cattle were present. We conclude areas surrounding water tanks in paddocks can be reservoirs of pathogenic bacteria. Presence of cattle, as well as muddy conditions, may influence the prevalence of E. coli O157:H7 in areas surrounding water tanks.