Changes over time of microbial load, surface free energy, and roughness of a variety of floor materials were investigated after hygiene operations in meat, pastry, and milk processing environments. Measurements were made in the laboratory on test plates which had been inserted in floors of food premises and subjected to the habitual fouling-cleaning cycles for up to 16 weeks. Microbial contamination of floor materials, assessed after sonication, appeared to be controlled in the milk site, which was generally dry. In both pastry and meat sites a specific microbial population developed and could stabilize to levels up to 10(4) and 10(6) CFU cm(-2), respectively. In the meat site bacterial contamination could be as high as 10(7) CFU cm(-2) on one rough floor material. After introduction in the premises, all flooring materials tended to have similar surface free energy values that could be simulated in the laboratory either perfectly by conditioning the surface with the treated food (in the case of the milk premises) or approximately by conditioning the surface with the hygiene agents used (in the case of the meat and pastry premises).