[EN] In this study, an analysis of the microbiological quality present in the bathing and transitional waters of the mouth and coastal area of the river Serpis was carried out. Specifically, six sampling points were analysed (current outfall outlet, 1 km south of the current outfall outlet, in the vicinity of the spillway, Marenys de Rafalcaid beach and Venecia beach). The presence of faecal contamination was determined by means of the parameters established in Royal Decree 1341/2007, of 11 October, on the management of bathing water quality. The presence of faecal contamination was determined by counting the forming units of three culture media, with the indicators Escherichia coli and Enterococcus faecalis. Considering the population and meteorological conditions, a high presence of faecal contamination was found at the current outfall outlet and in the vicinity of the spillway. Whereas, 1 km south of the current outfall, the Marenys de Rafalcaid beach and the Venecia beach did not show faecal contamination with excellent water quality. TFGM