The aim of this study was to investigate the ability of Proteus mirabilis to swarm over various types of urinary catheters. The test strain was found to swarm over catheters for distances of up to 10 cm within 24 h. Migration was significantly more rapid over hydrogel-coated latex catheters than over all-silicone or silicone-coated latex catheters. Scanning electron micrographs revealed discrete rafts of typically elongated swarmer cells on catheter surfaces. Migration of swarmers along catheters into the bladder could thus initiate Proteus mirabilis catheter-associated infections.