Profuse numbers of Enterobacteriaceae were found in samples of surface waters from the Ciliwung River and adjoining canals which criss-cross metropolitan Jakarta and are used widely for domestic purposes by the poorer sections of its population. 15 of the 20 specimens gres E. coli, Klebsiella were isolated from seven and Citrobacter from four. Using enrichment culture procedures, Salmonella sp. were grown from 10 (48%) of 21 water samples examined, and 12 (63%) of aquatic sediments collected at the same sites. Altogether 14 serotypes and 37 Salmonella isolations were recorded. This high degree of faecal contamination of the environment is a major cause of the immense problem of gastro-intestinal infections in that city and probably in many similar cities in developing countries in the tropics.