from the patient's anesthetic breathing circuit into the air of operating rooms during delivery of anesthesia. Personnel who are working in operating rooms are most likely to be exposed to waste anesthetic gases with no or bad automatic ventilation or scavenging systems. Aim of the work: The current study aimed to assess the level of biological marker of anesthetic gases and identify genotoxic effects among operating room nurses in Zagazig University Hospitals. Materials and methods: This study was conducted in Zagazig University Hospitals on 64 nurses who were divided into two groups: operating room nurses as exposed group, matched with outpatient clinic nurses as non exposed group. The data were collected using a questionnaire including demographic data, occupational, medical, family histories and complaints. Laboratory investigations done including Karyotyping of the chromosomes to assess genotoxic effects and assessment of urinary isoflurane. Results: Our study showed that there were highly statistical significant difference between both groups regarding occurrence of threatened and spontaneous abortion, repeated abortion> 2 times, congenital anomalies and symptoms during work as headache and dizziness. Also this work showed that chromosomal aberrations were present among about 59% of the exposed group, compared to 12.5% of non-exposed with highly statistically significant difference . The most common form of abnormalities were breaks of chromosomes (31.3%), fragments (18.8%) and polyploidy (6.2%). There were statistical significant difference between exposed and non-exposed in number of abnormal chromosomes and urinary isoflurane. Conclusion: Exposure to some anesthetic gases is associated with genotoxic effects among operating room personnel, leading to increased morbidity.