Several outbreaks of gastroenteritis related to the consumption of shellfish (frequently eaten raw) have been reported in different parts of the world. In Europe, hum an calicivirus infections may have been involved in winter outbreaks in recent years, although there is little evidence confirming such viral contamination in shellfish. This study presents the first results of a field survey on viral contamination in two shelllish harvesting areas along the French Mediterranean coast. The first, consisting mainly of oyster beds, was c1assified in category A, as determined by fecal coliform counts in shellfish (European Community Directive 91/492), and the second, a mussel bed, was c1assified in category C. Shelllish samples were collected monthly between August, 1995 and April, 1997, and RT-PCR was used to detect viruses known to be involved in outbreaks of gastroenteritis: enterovirus, human calicivirus, rotavirus, and astrovirus. Contamination by fecal coliforms was evaluated in the same samples. Virological results in shellfish were correlated with data on the incidence of epidemics of gastroenteritis in the coastal population obtained from a French survey. A relationship was observed between virological results and epidemiological data. For the 2 years when the incidence rate of gastroenteritis was maximal in win ter, the mussel bed \Vas always contanunated by the four types of viruses screened. Sinular results were observed for oyster beds during the second winter; whereas, two sampi es were lughly contarninated during the first winter, and a third showed low contamination (only rotavirus). These results suggest that an epidemic of gastroenteritis in the hum an population contributed ta viral contamination of the marine environment through discharge of waste water.