Abstract: Objective To understand the pathogen spectrum and epidemiological characteristics of infectious diarrhea in Shanghai from May to December, 2012. Methods A regular sampling survey was conducted among the infectious diarrhea cases seeking medical care in 6 hospitals at different levels randomly selected in Shanghai, and stool samples were collected from these cases for bacteriological and virological detections. Results Among 1001 stool samples detected, 465 were pathogen positive (46.45%). Seven kinds of bacteria, including Vibrio parahemolyticus (61 cases) and Salmonella (35 cases), and 5 kinds of viruses, including norovirus (262 cases) and rotavirus (40 cases), were detected. The bacterium positive rate was 12.09% and the virus positive rate was 32.07%. The positive detection rate was obviously higher in summer than that in autumn and winter. The average age of 465 positive cases were 44.20±17.56 years. The difference in age distribution between positive cases and negative cases was not statistically significant (P>0.05). More cases had abdominal pain and fever in bacteria positive group than in virus positive group, but less cases had nausea and vomiting in bacteria positive group than in virus positive group. More cases had dining together or travel history 5 days before onset in bacteria positive group than in virus positive group, and more cases had pet exposure in bacteria or virus positive group than in bacteria or virus negative group. All the differences were all statistically significant (PConclusion The pathogen spectrum of infectious diarrhea was wide and related seasonality was obvious in Shanghai. It is necessary to take pathogen and season specific prevention and control measures.