Pseudomonas aeruginosa resistant to both gentamicin and carbenicillin was isolated with increasing frequency at the Cincinnati Veterans Administration Hospital during the period 1971 to 1974. A comparison of patients from whom P. aeruginosa was isolated during this period failed to reveal any significant clinical differences between the patients colonized or infected with resistant organisms and those colonized or infected with susceptible organisms. Overt clinical infection attributable to either organism was rare. The antibiotic-resistant organisms were isolated most frequently from urine. Isolation of the antibiotic-resistant organisms was more frequent from patients who had previously received gentamicin.