Counts of Pseudomonas ueruginosa had a high positive correlation with counts of coliforms, fecal streptococci, presumptive pathogenic yeasts, and heterotrophic bacteria in surface waters of Rio de Janeiro. Pseudomonas aeruginosa counts were notably higher in fresh than in marine waters, and it was isolated from about 50% of marine and 100% of nonchlorinated freshwater samples that passed the fecal coliform based Brazilian bathing standards. The most probable number method for enumeration of P. aeruginosa contained this microbe in 90% of the positive tubes from freshwater samples, but it had reduced selectivity in marine waters with 37.5% false negative and 35% false positive results. Microbial indicators of fecal pollution were not effective for noting the presence of P. aeruginosa in freshwaters.