One hundred eight strains of Pseudomonas aeruginosa isolated from the patients (sputum, urine, burn skin, stool and blood) of Pusan National University hospital were tested for exonezyme production, antimicrobial susceptibility and serotyping. The results obtained were as follow: In exonezyme production test, 50 strains (46.30%) produced both protease and elastase. Thirty three strains (30.55%) did not produce any exoenzyme, 18 strains (16.67%) produced only protease and 7(6.48%) stains only produced elastase. As the result of antimicrobial susceptibility by the disc diffusion method, most strains were resistant to sulfamethoxazole (96.30%). But the resistant rate against gentamicin and ticarcillin were 47.23% and 46.30% respectively. The resistant rate to other antibiotics were less than 40%. All strains could be serologically typed. Most strains were identified as type Ⅲ: among them, 51 strains were belonged to serotype E. The correlation of serotype and exoenzyme production was not found.