Culture of flower vase water from wards in the David Lewis Northern Hospital, Liverpool, revealed large numbers of potentially pathogenic bacteria. The types of organisms isolated may reflect the particular ecology of this hospital as they differed in some ways from those reported from other centres. The incidence of wound infections during the period of study was low (5-2 per cent) despite the regular overgrowth of bacteria in flower vases, and there did not appear to be any definite correlation between the types of bacteria isolated from flower vase water and those responsible for wound infections. The addition of hydrogen peroxide to flower vases proved a very effective antiseptic and is recommended for general use as a precautionary measure.