Five urinary bladder incisions were performed in 16 rabbits and the defects closed by plain catgut 4-0, chromic catgut 4-0, polypropylene 4-0, polyglactin 910 4-0 and polyglactin 910 8-0 in the form of an all-layer suture, thereby obtaining a total of 80 suture sites. The running sutures in 8 animals were reviewed by light microscopy after 1, 2, 7 and 15 weeks, and in 8 additional animals after 3 days, 1, 2, 7 and 15 weeks by scanning electron microscopy. Moreover, we analyzed and compared the autopsy findings on gross inspection, the urinary sediments and urinary cultures of the individual animals. Scanning electron-microscopic evaluations showed that epithelization of the intraluminal suture portions can be accomplished after 3 days already. Reduced suture strength and rapid absorption of the suture material prevent later postoperative incrustations. Light-microscopic inspection of the segments of the bladder wall bearing this suture material suggests that a minor inflammatory tissue response around the suture material--with polyglactin 910 8-0 in particular--is more likely to enhance regeneration of the tunica muscularis and to prevent formation of cysts than seen with a long-standing highly inflammatory tissue response around the suture site of catgut threads. In the animal experiment, the polyglactin 910 suture has shown sufficient firmness and proved to be superior to any other suture material as regards the reaction to foreign bodies and inclination to incrustation.(ABSTRACT TRUNCATED AT 250 WORDS)