Our objective was to compare monofilament and multifilament tapes positioned without tension at the midurethra for postoperative complications and cure rate. One hundred patients with stress urinary incontinence were randomly allocated into two study groups. Using identical surgical methodology, 50 patients had a monofilament tape inserted at the midurethra using the TVT delivery instrument, and another 50 a multifilament tape using the IVS delivery instrument. The only significant difference between the groups was in the incidence of postoperative urinary retention ( p=0.023). Ten patients from the monofilament group required longer than normal ('normal' means to the morning of the next day) catheterization, in contrast to only two from the multifilament group. The clinical efficacy of both procedures was equally high. Conclusions were that both tapes appear to be equally effective in the surgical treatment of SUI. The higher incidence of postoperative urinary retention in the monofilament group was most likely caused by the elastic feature of this tape.