To study the adhesion capability of seven strains of Listeria monocytogenes to polystyrene and stainless steel surfaces after cultivation at various NaCl concentrations. Determination of growth limits indicated that all seven strains were able to grow in up to 11% NaCl in rain heart infusion and 3 g l(-1) yeast extract-glucose at 20 degrees C, but no growth was detected at 15% NaCl. Adhesion of L. monocytogenes was estimated after 4-h incubation at 20 degrees C in 96-well microtitre plates. Statistical results revealed no significant difference between adhesion to polystyrene and stainless steel although surface properties were different. Adhesion between 0% and 6% NaCl was not different, whereas adhesion at 11% NaCl was significantly lower. This discrepancy in adhesion was correlated with the down-regulation of flagella at 11% NaCl. Only high salinity levels, close to nongrowth conditions, repressed the expression of flagella, and consequently, decreased the adhesion capability of L. monocytogenes. Adhesion of L. monocytogenes to inert surfaces depends on environmental conditions that affect flagellum expression. High salinity concentrations would delay biofilm formation.