The influence of preventive administration of Lactobacillus casei subsp. casei and maltodextrin KMS X-70 on Escherichia coli 08: K88 adhesion in the gastrointestinal tract of 11 conventional and 6 gnotobiotic piglets was investigated. The preventive administration of L. casei alone had almost no inhibitory effect on the adherence of E. coli to the jejunal mucosa of gnotobiotic and conventional piglets while the lactobacilli administered together with maltodextrin decreased the number of E. coli colonising jejunal mucosa of gnotobiotic piglets by 1 logarithm (4.95 log 10/cm2) in comparison with the control group (5.96 log 10/cm2). L. casei administered in combination with maltodextrin decreased the number of E. coli colonising the jejunum of conventional piglets by more than two and half logarithm (4.75 log 10/cm2, p < 0.05) in comparison with the control (7.42 log 10/cm2). The inhibitory effect of Lactobacillus casei and maltodextrin KMS X-70 on the adhesion of E. coli to the intestinal mucosa of conventional and gnotobiotic pigs was probably mediated by Lactobacillus--produced antibacterial substances and stimulation of immunity.