Previous studies performed in our laboratory have indicated that the primary antibacterial defense mechanism of the rabbit urinary bladder is the antiadsorptive action of the surface mucopolysaccharide. Removal of this layer with an acid rinse increases bacterial adherence up to 100 fold. Exogenous mucopolysaccharide (heparin) has been shown to restore Escherichia coli adherence to control levels. To determine whether this antiadherence action of heparin is species specific, we compared the adherence of 5 common urinary tract pathogens (Escherichia coli, Klebsiella ozonae, Proteus mirabilis, Pseudomonas aeruginosa, and Streptococcus fecalis) to both mucin intact and mucin deficient rabbit bladders with and without prior heparin exposure. Bacteria were radiolabeled by addition of 3H-adenine to the culture broth so that the number of bacteria adhering to the bladder could be determined using liquid scintillation spectrophotometry. Results were as follows: Acid removal of the mucin layer significantly increased the adherence approximately 10 fold for all 5 species tested. Briefly exposing the mucin deficient bladders to heparin decreased the adherence of all species tested except Pseudomonas to mucin intact control levels. Heparin treatment of mucin intact bladders slightly decreased adherence of all species except Pseudomonas below mucin intact controls, however, results were not statistically significant. The magnitude of Klebsiella adherence was nearly 20 fold greater than all other species tested. While this non-species specific adherence inhibition of heparin may prove useful in the clinical setting, it appears to be less effective against Pseudomonas.