More evidence is emerging on the importance of the clinical environment in encouraging hospital infection. This review considers the role of cleaning as an effective means to control infection. It describes the location of pathogen reservoirs and methods for evaluating hospitals' cleanliness. Novel biocides, antimicrobial coatings and equipment are available, many of which have not been assessed against patient outcome. Cleaning practices should be tailored to clinical risk, given the wide-ranging surfaces, equipment and building design. There is confusion between nursing and domestic personnel over the allocation of cleaning responsibilities and neither may receive sufficient training and/or time to complete their duties. Since less labourious practices for dirt removal are always attractive, there is a danger that traditional cleaning methods are forgotten or ignored. Few studies have examined detergent-based regimens or modelled these against infection risk for different patient categories. Fear of infection encourages the use of powerful disinfectants for the elimination of real or imagined pathogens in hospitals. Not only do these agents offer false assurance against contamination, their disinfection potential cannot be achieved without the prior removal of organic soil. Detergent-based cleaning is cheaper than using disinfectants and much less toxic. Hospital cleaning in the 21st century deserves further investigation for routine and outbreak practices.