tBackground: In Brazil, ventilator-associated pneumonia (VAP) caused by carbapenem resis-tant Acinetobacter baumannii and Pseudomonas aeruginosa isolates are associated withsignificant mortality, morbidity and costs. Studies on the clonal relatedness of these isolatescould lay the foundation for effective infection prevention and control programs.Objectives: We sought to study the epidemiological and molecular characteristics of A. bau-mannii vs. P. aeruginosa VAP in an adult intensive care unit (ICU).Methods: It was conducted a cohort study of patients with VAP caused by carbapenem resis-tant A. baumannii and P. aeruginosa during 14 months in an adult ICU. Genomic studies wereused to investigate the clonal relatedness of carbapenem resistant OXA-23-producing A.baumannii and P. aeruginosa clinical isolates. The risk factors for acquisition of VAP were alsoevaluated. Clinical isolates were collected for analysis as were samples from the environ-ment and were typed using pulsed field gel electrophoresis.Results: Multivariate logistic regression analysis identified trauma diagnosed at admissionand inappropriate antimicrobial therapy as independent variables associated with the devel-opment of A. baumannii VAP and hemodialysis as independent variable associated with P.aeruginosa VAP. All carbapenem resistant clinical and environmental isolates of A. baumanniiwere OXA-23 producers. No MBL-producer P. aeruginosa was detected. Molecular typing revealed a polyclonal pattern; however, clone A (clinical) and H (surface) were the most frequent among isolates of A. baumannii tested, with a greater pattern of resistance than other isolates. In P. aeruginosa the most frequent clone I was multi-sensitive. Conclusion: These findings suggest the requirement of constant monitoring of these microor- ganisms in order to control the spread of these clones in the hospital environment.