Using standard bacteriological procedures, 403 cockroaches (Blattella germanica) collected in Tripoli, from hospitals or the households surrounding the hospitals, were examined for bacteria that are potentially pathogenic to humans. Almost all of the cockroaches (96.1% of the 253 from hospitals and 98.7% of the 150 from households) were found to be carrying potentially pathogenic bacteria, with similar mean burdens of 3.2 x 10(5) colony-forming units (cfu) (range=0-1.4 x 10(7)) for each hospital cockroach and 1.9 x 10(5) cfu (range=0-3.1 x 10(6)) for each household cockroach (P>0.05). Overall, 27 and 25 species of potential pathogen were isolated from the hospital and household cockroaches, respectively, with Klebsiella, Enterobacter, Serratia and Streptococcus predominant. Carriage of species of Serratia was significantly more common among the hospital cockroaches than among the household cockroaches, whereas carriage of Klebsiella, Enterobacter, Citrobacter and Aeromonas was significantly more common among the household cockroaches than among the hospital. Multiple resistance, to at least six different antibiotics, was more commonly observed among the enteric bacteria isolated from the hospital cockroaches than among those recovered from the household cockroaches. Overall, >30% of the isolates of Enterobacteria recovered were each resistant to at least four antimicrobial agents, and 95% of the Pseudomonas isolates were each resistant to at least eight such agents. Cockroaches may play an important role in the spread of multiple-antibiotic-resistant, bacterial pathogens within the hospitals and surrounding communities of Tripoli and other, similar cities. The local health and environmental authorities need to be encouraged to treat B. germanica infestations seriously and to control them quickly and effectively.