Statement of Problem: Oral biopsy is important in the definite diagnosis of oral and maxillofacial lesions. This procedure as well as other laboratory services is prone to errors affecting the patients' safety.Purpose: The purpose of this study was to evaluate pre-analytical biopsy specimen errors in the Oral Pathology Laboratory of Hamedan School of Dentistry, west of Iran.Materials and Method: Ninety-one oral biopsy samples, obtained from departments of oral and maxillofacial surgery (34 samples, 37.3%), oral medicine (22 samples, 24.3%) and periodontics (10 samples, 10.9%), as well as private offices (16 samples, 17.6%) and hospitals (9 samples, 9.9%) were received and evaluated in the Oral Pathology Laboratory of Hamedan School of Dentistry considering pre-analytical errors. Results: The errors in the request forms included unmentioned names of patients (7.7%), age (3.3%), clinical history (4.4%), site of biopsy (10.9%), differential diagnos-is (18.7%) and the name of the requesting clinician (8.8%), as well as lack of radiographs (4.4%) and previous biopsy results (2.2%). Use of inappropriate fixative (5%), and specimen-containers with non-proportional volume (3%), and their small size inlets (3%) was also reported. Non-standard containers were seen in 19% of the cases, and mislabeling errors (31 missed, 2incomplete defects, and 1 incorrect) in 34% of the cases. Of 105 specimens, 6.67% were small in size, 1.90% superficially removed, and 0.95% had been traumatized. Out of the 5 containers with more than one specimen, 4 containers did not have any markers.Conclusion: Considering the biopsy errors in the study specimens, training and surveillance to reduce the frequency of such errors seems necessary.