An investigation on the hygienic quality of the Tiber river was conducted with the aim both to enumerate Giardia cysts and Cryptosporidium oocysts in the water and to determine possible correlations between them and bacterial indicators, pathogens and physico-chemical parameters. A low hygienic water quality was evidenced, with high counts of microorganisms. Furthermore, variable concentrations of Giardia and Cryptosporidium were observed. No correlation was found between the protozoa concentrations and that of the other microorganisms, whilst a significant correlation with redox potential and Giardia cysts was calculated.