Four hundred and sixty-four Pseudomonas aeruginosa strains were isolated in northern Lebanon at the Islami Hospital Microbiology department, in Tripoli. The purpose of this study was to evaluate the susceptibility of these strains to antibiotics, to compare this susceptibility according to the nature of the sample and the year of sampling. The results show that urinary samples were the most frequent (39.3%), followed by wound samples (21.2%), and ear samples (16.5%). The average rate of susceptible strains was 39.8% to ticarcillin, 56.9% to piperacillin, 58.2% to piperacillin + tazobactam, 74.1% to imipenem, 63.3% to ceftazidime, 60.4% to cefepime, 62.1% to aztreonam, 60.3% to netilmicin, 57.5% to gentamicin, 62.2% to tobramycin, 69% to amikacin, 100% to colistin, 45.4% to pefloxacin and ofloxacin, 57.7% to ciprofloxacin and 1.3% to rifampicin. The study showed that the strains isolated from pulmonary secretions were the most resistant to antibiotics.