Molecular-epidemiological analysis of Pseudomonas aeruginosa isolated from cockroaches captured in hospitals and from patient urine was performed, employing randomly amplified polymorphic DNA (RAPD) analysis to investigate the usefulness of RAPD analysis. Four specific bands at positions of 993, 875, 521, and 402 bp were commonly detected using primer 272 in 16 of 45 cockroach-derived strains (35.6%), but not in 21 urine-derived strains. On analysis using primer 208, 4 specific bands at positions of 1,235, 1,138, 1,068, and 303 bp were commonly detected in 15 of the 45 cockroach-derived (33.3%) and 10 of the 21 patient urine-derived (47.6%) strains, in a total of 25 of 66 strains (37.8%). On cluster analysis, 12 (48.5%) and 16 (66.7%) clusters were grouped based on a homology of 89% or greater, using primer 272 and primer 208, respectively, showing that primer 208 was suitable for the confirmation of diversity. Seven patterns were clustered based on 100% homology using either primer, and 6 of these consisted of only cockroach-derived strains. In the individual groups with 100% homology, all strains in the group were isolated at an identical site during the same period. P. aeruginosa isolated from cockroaches showed diverse genotypes suggesting several sources of contamination, indicating the necessity for investigating infection control targeting cockroaches inhabiting hospitals.