The aim of the present study was to evaluate the presence anti- E. coli, -rotavirus and -coronavirus, in calves' sera. A total of 184 calves under 1 month of age (84 diarrheic & 100 normal) was studied. Serological tests including: direct ELISA for detection of anti-K99 E. coli, - rotavirus and - coronavirus and tube agglutination test for detection anti-O157 E. coli, antibodies were used. Data were analyzed by chi-square, fisher test and t-student tests. Anit-K99 E. coli antibodies were detected in 56% and 66% of diarrheic and normal calves, respectively. Tube agglutination test showed the presence of anti-O157-E. coli antibodies in 82% and 69% of diarrheic and normal calves respectively. Anti-rotavirus antibodies were detected in 100% and 99% of diarrheic and normal calves, respectively. Anti-coronavirus antibodies were detected in 82% and 72% of diarrheic and normal calves respectively. Conclusion: The results of the present study may indicate the high exposure of the examined dairy cattle population to E. coli, rotavirus and coronavirus and also the absence of correlation between such serological responses with the prevention of calves' diarrhea.