In this study, the protective effect of specific egg yolk antibodies on diarrhea caused by Escherichia coli K88 (F4) was investigated with 179 weaning piglets in a double-blind field trial. The piglets were divided into three groups. The antibody group received egg powder with specific antibodies to E. coli K88, K99, 987P, and rotavirus, while one control group was fed with egg powder without specific antibodies and a second control group received no egg powder at all. The piglets were fed ad libitum. The egg powder was offered in a 5% feed ration. Compared with the control groups, the piglets of the antibody group showed significant differences (P < 0.05, chi 2-test) in the parameters rate of diarrhea (17.2%) (antibody group) to 60.7% (control egg group) or 56.7% (control group without egg powder), severity of symptoms (5.2-39.3% or 26.7%) and frequency of additional treatments (8.6-55.7% or 51.7%). Because of the additional treatments, no difference could be found in body-weight gain. In control groups, three piglets died, while no pigs died in the antibody group.