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Abstract Background and Objective: Laboratory personnel have always accidental exposure to clinical samples, which can cause the transmission of infection. This threat can be prevented and controlled by education for the use of safety instruments. The purpose was to determine the frequency of accidental exposure to laboratory samples among Yazd laboratory personnel in 2011. Material and Methods: This descriptive cross-sectional study was conducted on 100 of Yazd clinical laboratory personnel. The data was collected, using a valid and reliable questioner, via interview and analyzed by means of SPSS software. Results: Eighty-six percent of the subjects reported an experience of accidental exposure to clinical samples, such as blood, serum and urine. The causes were carelessness (41%) and work overload (29%). Needle- stick was the most prevalent injury (52%) particularly in sampler workers (51%) and in their hands (69%). There wasn’t significant relationship between accidental exposure to laboratory samples and the variables such as private and governmental laboratories (p=0.517), kind of employment (p=0.411), record of services (p=0.439) and academic degree (p=0.454). The subjects aged 20-29 (p=0.034) and worked in sampling unit had the highest accidental exposure. Conclusion: Based on the results, inexperience of the personnel especially in sampling room, overload at work and ignorance of applying safety instruments are known as the most important reasons for accidental exposure to clinical samples. Keywords: Contamination Accidental Exposure Infectious Agents Laboratory Personnel