Objective: In this study, the presence of PER-1 type extended spectrum beta lactamases (ESBL) was investigated in ceftazidime-resistant Acinetobacter baumannii strains isolated from bloodstream infections by polymerase chain reaction (PCR), and the clonal relation of the isolates was investigated by random amplified polymorphic DNA (RAPD) PCR and pulse-field gel electrophoresis (PFGE) in all PER-1 producing A. baumannii strains. Material and Methods: The isolates were identified as A. baumannii by conventional methods and Phoenix 100BD automated system (Becton Dickinson Diagnostic Systems, Sparks). Ceftazidime resistance was determined by E test method and PER-1 genes were screened by PCR in ceftazidime resistant strains. Genetic relation of PER producing A. baumannii was investigated with RAPD and PFGE, and the similarity of the bands were calculated according to "dice similarity coefficients". Colistin susceptibility test was studied by E-test, and other antibiotic susceptibility tests were performed by the Kirby-Bauer disk-diffusion method according to the standards of Clinical and Laboratory Standards Institute. Results: Of the 100 A. baumannii isolates; 78 were determined as ceftazidime-resistant. The PER-1 gene was identified in 18 (23%) isolates of these strains. The clonal relation of the 18 PER-1 positive isolates were investigated by RAPD and PFGE. All PER-1 positive isolates were found to be clonally related. The resistance rates of the A. baumannii strains were found as follows: 67% to amikacin, 71% to imipenem, 85% to ciprofloxacin, 83% to tetracycline, 83% to trimethoprime-sulfamethoxazole, 87% to cefepim, 99% to piperacillin-tazobactam and 100% ceftriaxone. Colistin resistance was not determined. Conclusion: In our study, the prevalence of PER-1 was lower than the previous studies. However, presence of the high ceftazidime resistance rates among these isolates may indicate the presence of other beta-lactamases. Detection of clonally-related isolates with RAPD and PFGE in different clinics may be due to treatment of these patients in the same clinic before, and this may explain the spread of PER-1 positive strains. © 2013 by Türkiye Klinikleri.