Two decades of research have established newer pathogens and techniques in establishing several organisms of diarrhoeal diseases as aetiological agents. It is now possible to detect an agent in 80% of the situation of diarrhoea in a standard laboratory. The brief review describes the list of pathogens, their diagnostic techniques with short description on clinical and epidemiological status. In the early 1980s, microbiologists could isolate the causative agent of diarrhea in only 20% of cases, but now they can isolate an agent in about 80% of cases. Since then, they have identified more enteropathogens. In fact, 25 enteropathogens cause disease. Shigella species tend to afflict people in unhygienic areas with watery or mucoid diarrhea. They tend to strike infants during weaning. They often are resistant to several drugs, particularly nalidixic acid. IN 1984, S. dynsenteriae type 1 struck people in West Bengal, Assam, and Orissa, India. Salmonella species are other common agents of diarrhea. Unlike Shigella species, the infective dose for Salmonella is rather small. Food is the chief mode of transmission. In the early 1990s, they were responsible for considerable diarrhea morbidity in parts of West Bengal. birds carry Campylobacter, but person to person transmission occurs in nurseries. Studies in Calcutta indicate considerable asymptomatic infection of C. jejuni in 5 year old children. The enterotoxin of several types of Vibrio cholerae continues to cause outbreaks of profuse watery diarrhea. Vibrio parahaemolyticus dwells in marine animals and infection favors adults. In Calcutta, it is the 2nd most common health hazard and is present year round. Different strains of Escherichia coli cause diarrhea including enteropathogenic, enterotoxigenic, enteroinvasive, enterohemorrhagic, and enteroadherent E. coli.. A study published in 1984 indicates that, in Calcutta, enterotoxigenic E. coli was present in 12.1% of the feces of diarrhea patients from all age groups. Yersinia and Aeromonas species are also bacteria which cause diarrhea. Rotavirus is a common virus causing diarrhea. In India, Manipur and Calicut experience rotavirus epidemics every winter. Protozoans also cause significant diarrhea including Entamoeba histolytica, Giardia lamblia, and Cryptosporidium species.