Previous investigations have shown that certain strains of Lactobacillus species act as probiotic organisms within the gastrointestinal tract, helping to reduce colonization and infection with potential enteric pathogenic bacteria. Two potentially debilitating enteric pathogens, Entertoxigenic Escherichia coli and Enterohemorrhagic Escherichia coli, affect millions of people worldwide; however data on the effectiveness of probiotics for these strains of E. coli are minimal. In this study, we investigated the inhibitory effect of four Lactobacillus species against the growth of these two pathogenic strains of E. coli, as well as E. coli 25922, a typically non-pathogenic strain. The amount of growth inhibition was determined using both live lactobacilli cultures and supernatant obtained from actively growing lactobacilli broth cultures. The amount of growth inhibition of each E. coli strain varied depending on the method as well as the species of Lactobacillus used. Our experimental findings suggest that Entertoxigenic E. coli was strongly inhibited when exposed to live lactobacilli cells, but only partially inhibited when exposed to supernatant alone. In contrast, Enterohemorrhagic E. coli was equally inhibited by exposure to live cells or supernatant. More data are needed to determine the clinical implication of our experimental results.