Abstract Diagnostic error in surgical pathology can be detrimental to patients. In the past 10–20 years there has been accumulation of knowledge that helps pathologists understand how errors occur and how they can be avoided. While there are multiple types of errors including specimen identification, specimen processing and transcription errors, interpretive diagnostic errors tend to account for the majority of errors that affect the patient's course. As such, this article is focused on diagnostic interpretive errors. Five factors are involved in determining and avoiding errors. These factors include: (1) knowledge, experience and training; (2) standardization of procedures and terminology; (3) clinical history and clinical correlation; (4) ancillary studies; and (5) redundancy or case reviews. These five factors and their contribution to errors and error avoidance is discussed.