Escherichia coli 08 was the most frequent coliform isolated from the blood and liver of morbid and dead neonatal, colostrum-free piglets raised under extremely sanitary conditions. This strain accounted for 67 per cent of the typable E. coli. The next most numerous strain occurred at a frequency of 6 per cent. Hence, E. coli 08 was considered the main coli enteropathogen in our experimental, isolated environment. In random samples of the feces of healthy and diarrhetic neonatal piglets, 24 per cent of the typable E. coli was type 08. When a directed effort was made to isolate E. coli 08 from the feces of neonatal piglets in a healthy, colostrum-free litter, this strain was isolated from 17 per cent of the total E. coli colonies examined. Thus, the enteropathogen E. coli 08 was ubiquitous in the feces of piglets in our environment, making up approximately 20 per cent of the fecal E. coli. 85 per cent of the bacteremia and death in which E. coli was isolated from blood or liver occurred in piglets fed diets void in bovine and porcine gamma globulin. Tube agglutination tests demonstrated that agglutinins to E. coli 08, and other serotypes as well, were present in bovine colostrum and to a lesser extent in porcine colostrum. These agglutinins were practically lacking in solutions of porcine and bovine gamma globulin. Feeding 10(9)E. coli 08 bacteria to 2-week-old, colostrum-free, gamma globulin-free, 08 agglutinin-free piglets did not produce visible disease.