As the European Union revises the 1975 directive establishing standards for bathing waters, the Ministry of Health seeks to identify the most relevant microbiological parameters for monitoring bathing water quality and to determine the risk levels associated with different values that could form the basis of the new standards. In this context, the InVS conducted research to: 1) characterize the dose-response relationships between the levels of microbiological indicators identified in the literature and the occurrence of digestive disorders, and 2) assess the risk of digestive morbidity associated with different levels of contamination. A meta-analysis of epidemiological studies published in the international literature was conducted. The risks attributable annually to swimming were established for different categories of disorders, for increasing levels of water contamination with fecal coliforms and fecal streptococci. Freshwater contamination levels of 10 bacteria per 100 ml result in the most credible attributable risks of digestive disorders of 2 per 10,000 people per year for fecal coliforms and 2 × 10⁻³ for fecal streptococci. At a level of 100 bacteria per 100 ml, these annual attributable risks rise to 10⁻³ and 1.3 × 10⁻² respectively. In conclusion, it is recommended to retain fecal coliforms and fecal streptococci as indicators of digestive morbidity, as these are the most predictive parameters of infectious digestive risk based on current knowledge. The establishment of new standards depends on the acceptable level of risk, given that the usual frequency of disorders in the general population is in the range of 0.2 to 2.8 annual events per person, depending on the type of morbidity considered. (R.A.)