Although listeriosis is a rare cause of human disease in the United Kingdom, an increase in the number of cases has been observed since 2001, almost exclusively in persons older than 60 years. This increase prompted this study on the microbiological safety of ready-to-eat (RTE) foods, which included those types potentially linked to cases of listeriosis. Between May 2006 and April 2007, 6,984 RTE foods were sampled (2,168 sliced meats, 1,242 hard cheese, 1,088 sandwiches, 878 butter, 725 spreadable cheese, 515 confectionery products containing cream, and 368 probiotic drinks). The food types with the highest prevalence of Listeria monocytogenes were sandwiches (7.0%) and sliced meats (3.7% within shelf life, 4.2% end of shelf life). L. monocytogenes at > 100 CFU/g (exceeding the European Commission's food safety criteria limit) only occurred in sandwiches (0.4%) and sliced meats (0.7% within shelf life, 1.0% end of shelf life). Contamination with L. monocytogenes at >100 CFU/g was more frequent in meats that were prepacked and/or of pack size > or = 300 g and in sandwiches that were supplied prepacked that contained salad vegetables as an ingredient. Satisfactory microbiological quality was associated with premises on which the management was trained in food hygiene and those that complied with hazard analysis and critical control point principles. This study provides important information about the microbiological safety of RTE foods and demonstrates that the control of L. monocytogenes in such foods, and in particular sandwiches and sliced meats, is essential in order to minimize the risk of this bacterium being present at levels hazardous to health at the point of consumption.