In vitro adherence of the nosocomial pathogens Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, and Candida albicans to select radiopaque silicone compounds was lower than that observed for the base silicone (p < 0.03). Except for E. coli ATCC 11775 and Candida albicans, all microorganisms showed significantly lower adherence to a silicone compound impregnated with tantalum in comparison with a silicone compound impregnated with barium sulfate (p < 0.05). Surface hydrophobicity of the silicone compounds did not show a direct correlation with the concentration of radiopacity additives or with degree of bacterial adherence. Scatchard analyses of data indicated that the number of adherence sites for P. aeruginosa on the base silicone, BaSO4- silicone, and Ta-silicone were 9.2 x 10(6) per mm2, 6.1 x 10(6) per mm2, and 3.7 x 10(6) per mm2 respectively. As determined by the Langmuir adsorption isotherm, the dissociation constants for adhered P. aeruginosa to the base silicone, BaSO4-silicone, and Ta-silicone were 2.50 x 10(3) mm4, 1.45 x 10(3) mm4, and 6.27 x 10(3) mm4 respectively. Pseudomonas aeruginosa demonstrated first order kinetics of adherence to the silicone compounds with a half saturation time of 4.15 h for the base silicone, 1.06 h for the BaSO4-silicone, and 2.14 h for the Ta-silicone. The use of Ta-silicone stents may delay the development of ascending urinary tract infections.