We have previously reported that the administration of a competitive exclusion culture (PCF-1), derived from the cecal microflora of a young, healthy pig and maintained in a continuous flow fermentation system to neonatal pigs resulted in a decrease in the incidence of fecal shedding and cecal colonization by Salmonella choleraesuis in pigs at weaning. In the present experiment, we describe the effects of the administration of a derivative of the PCF-1 culture, RPCF, against an enterotoxigenic E. coli infection in neonatal pigs raised off-sow. The administration of RPCF at 12 and 24 hours after birth resulted in significant (P < 0.05) reductions in mortality, incidence of fecal shedding, and in gut colonization by E. coli when compared to control values. The RPCF reduced mortality from 17.5%, observed in untreated pigs, to 4.4% in RPCF-treated pigs. Fecal shedding of E. coli was reduced significantly (P < 0.05) in RPCF-treated pigs between Days 1 and 3 post-challenge. These results indicate that the RPCF culture is effective against one of the most important causes of neonatal scours (E. coli infections) in piglets.