The aim was to investigate the presence of leptospira infection and the antibiotic resistance of Enterobacteriaceae among wild rats living in a densely populated area. For this purpose 3-4 large traps were placed daily across the commercial port-front of Piraeus for the duration of two months. The rats captured were transferred in the laboratory alive, where samples were freshly collected. None of the 25 rats captured was found to be infected with leptospira. Only one rat was infected with Salmonella. Other predominant members of the family of Enterobacteriaceae were Escherichia coli, Proteus spp. and Klebsiella spp. Resistance to antimicrobial agents commonly used in veterinary treatment was very high for spectinomycin, erythromycin, neomycin and tetracycline in all tested species of Enterobacteriaceae. It appears that port rats living in the densely populated area of the city of Piraeus could become a source of infection for man and animals with microorganisms highly resistant to antimicrobial agents.