In vivo tissue responses were compared for three commercially available polypropylene suburethral slings that differ markedly in fabric structure and in size of resulting interstices and pores. All three elicited the same basic inflammatory response; however, individual fabric structures produced distinct differences in tissue formation within each mesh. The presence of numerous, closely spaced, small diameter filaments prevented formation of extensive fibrous connective tissue within two slings (ObTape and IVS Tunneller mesh). The much larger diameter monofilament and open knit structure of the Monarc sling permitted the most extensive fibrous tissue integration. These differences may be of interest to physicians considering clinical use.