The ability of the Lactobacillus acidophilus RC14 biosurfactant 'surlactin' to inhibit the initial adhesion of various uropathogenic bacteria and two yeast strains to silicone rubber was investigated in a parallel-plate flow chamber in filter-sterilised pooled human urine. A parallel-plate flow chamber with a silicone rubber bottom plate was filled with a 1.0 mg/ml biosurfactant solution for adsorption overnight (18 h). Subsequently, the adhesion of the bacterial or yeast cells from a urine suspension under low flow (shear rate 15 s(-1)) was followed in situ by automated image analysis. Control tests were with untreated silicone rubber. Initial deposition rates and numbers of adhering cells after 4 h of flow were determined. Surlactin layers caused a marked inhibition of the initial deposition rates and adhesion numbers after 4 h for the majority of the bacteria (11 of 15 strains tested) and this inhibition was particularly effective against Enterococcus faecalis, Escherichia coli and Staphylococcus epidermidis. Although the initial deposition rates of the two Candida albicans strains were reduced by c. 50% in comparison with the controls, the numbers of yeast cells adhering after 4 h were similar.