We researched the microbial etiology of 5,836 diarrheal processes in outpatients and inpatients at the Social Security Hospital in Cádiz, for the purpose of evaluating their microbiological and epidemiological characteristics. Bacterial gastroenteritis accounted for 51.6% of the cases, while 31.7% were viral and 16.6% were protozoal in origin. Salmonella enterica (35.6%) is the most frequently involved microorganism, especially in the summer, followed very closely by Rotavirus (31.7%). The incidence of Campylobacter jejuni (13.8%) and Cryptosporidium (7.1%) is also important. Due to the influx of tourists and their consumption of seafood, eggs and derivatives, acute gastroenteritis is a frequent pathology in our city. The number of cases has increased in recent years, and those of an infectious nature represented 27.2% of all cases recorded for the period 1988-1989.