Little is known about the effectiveness of the cleaning and disinfection methods used on commercial pig farms either in Ireland or worldwide. A National Salmonella Control Programme was implemented in Ireland in August 2002 to monitor and control the infection of pigs with Salmonella species. Commercial pig herds must be categorised according to their Salmonella status as either category 1, 2 or 3, having a serological prevalence of infection with Salmonella serotypes up to 10 per cent, between 10 and 50 per cent or more than 50 per cent, respectively. The aim of this study was to assess the efficacy of washing and disinfecting finisher units on category 1 and category 3 farms in reducing or eliminating the levels of contamination. Counts of Enterobacteriaceae were used as indicators of the contamination of the environment with enteric bacteria, which could include Salmonella species. Samples were taken from the pen floors, feeders and drinkers of seven category 1 and seven category 3 farms, and Enterobacteriaceae and salmonellae were enumerated in each sample. The results suggested that intensive cleaning and disinfection was effective at reducing levels of Enterobacteriaceae on the pen floors of both categories, but that residual contamination remained on the surfaces of the feeders and drinkers on all the farms, particularly on the category 3 farms.