The purpose of this study was to examine the effects of physical configuration and the chemical nature of suture materials on the preferential adherence of bacteria. Ten suture materials of 2-0 (chromic catgut, Dexon, Vicryl, PDS, Mersilene, Tycron, Ethibond, Surgilon, Ethilon, and Prolene) were used. The bacterial strains tested were Staph. aureus and E. coli. The level of bacterial adherence was determined quantitatively by radiolabelled cells and qualitatively by scanning electron microscopy. It was found that the amount of adhered bacteria depended on the type of suture material, the type of bacteria, and the duration of contact. In the group of absorbable sutures, the new PDS sutures exhibited the smallest affinity toward the adherence of both E. coli and Staph. aureus. Dexon sutures had the highest affinity toward these two bacteria. With nonabsorbable sutures, the physical configuration of the sutures contributed more to their ability to attract bacteria than the surface finish. The bacterial adherence on suture materials was also time dependent. Scanning electron microscope morphologic observation also indicated that Staph. aureus adhered on the suture surface in clusters whereas E. coli tended to adhere individually.