The incidence of antibiotic resistance and of R-factors in the faecal coliform populations of raw hospital and city sewage was investigated in Galway city. During a 14-month sampling period, the incidence of faecal coliform resistance to ampicillin, tetracycline, chloramphenicol and streptomycin in city sewage was on a par with, and in some cases, greater than the incidence in hospital sewage. Over 90% of resistantE. coli isolates from hospital and city sewage were simultaneously resistant to two or more antibiotics. In the majority of isolates, resistance was R-factor carried, with 90% of the city sewage isolates and 69% of the hospital sewage strains capable of conjugal transfer to a sensitiveE. coli recipient. The data indicates the presence of an undesirably high level of transferable antibiotic resistance in the gut flora of the healthy non-hospitalized population in Galway.