Approaching the problem of how close the sporadic diarrhea diseases correlate with epidemics of infectious diarrheas, including food poisonings, bacteriological studies were made on the characteristics of sporadic diarrheas in the past 10 years and analyzed. In collaboration with physicians, mostly pediatricians, in Oita district during 1985 to 1986 and 1989 to 1996, a total of 1707 specimens was obtained from diarrhea patients, suspected of bacterial cause. We have isolated 717 strains from 670 specimens (ca 40% of the total). The majority were; Campylobacter, Salmonella and EPEC with the rate of about 40, 24 and 23% respectively. On the other hand, isolation of Vibrio spp. and Staphylococcus were very few. The yearly trend of detection rates of such major agents were as follows: Campylobacter had the highest rate in the early period, 1989, but thereafter tended to decrease. In contrast, Salmonella continued to increase in rate through the study period until the present when it exceeds that of Campylobacter. This alternation is due primarily to the rapid increase of S. Enteritidis since its recent appearance. VTEC stays at a low rate with a slow increase showing no prevalence so far. From the above results the following may meet with attention. Vibrios and Staphylococci, known as popular agents for food poisonings, seem unlikely to correlate with sporadic diarrheas. Instead, the evidence that recent food poisoning is often represented by Salmonella, especially S. Enteritidis, suggests that epidemics of infectious diarrhea may be attributed to the background of common sporadic diarrheas.