Abstract Samples of fresh vegetables fed to patients in an Oncology and a University Hospital were examined for frequency of recovery and counts of Pseudomonas aeruginosa. Thirty-eight isolates from vegetables as well as 98 clinical isolates recovered during the same period of vegetable collection were serotyped and assayed for pyocin production in order to evaluate the role of vegetables as a source of microorganisms. Pseudomonas aeruginosa was recovered from 19·0% of the vegetable samples. Although 1% hypochlorite solution was used as a sanitizer, 50% of the positive samples were found to harbour more than 100 colony-forming units (ctu) g −1. Lettuce, chicory and watercress yielded the highest frequencies of isolation ( P < 0·05). The pyocin typing and serotyping of clinical strains revealed some types identical to those recovered from vegetables. Among those found in the University Hospital, serotype O4 and pyocin type PT10/b were detected in vegetables and in clinical specimens whereas types O1-PT22/e, O2a-PT10/a, O2a-PT10/b, O4-PT10/a, O11-PT10/a and O11-PT10/b were common in both groups of strains isolated in the Oncology Hospital. Our results strongly suggest that vegetables represent a source of endemic infection with P. aeruginosa for hospitalized patients.