Introduction: Formaldehyde (FA) is a high-production-volume chemical with a wide array of uses. Recently, it was re-evaluated for its carcinogenic effects and reclassified as humans carcinogen (Group 1) based on sufficient evidence in human and experimental animal studies. Aim of the work: to evaluate the pre-carcinogenic effects of formaldehyde among medical personnel in The Histopathology Laboratory. Materials and Methods: The study was conducted in histopathology laboratory including 30 workers occupationally exposed to formaldehyde and 29 persons matching with the exposed group for age, sex and socioeconomic status with no history of occupational exposure to formaldehyde. A questionnaire was done including inquiries about age, sex, occupational history and special habits. All participants were subjected to the following laboratory investigations: measuring DNA protein crosslink (DPC) and protein 53 (p53) both mutant and wild type. Results: This study shows statistically significant increase in symptoms and signs of respiratory and eye and skin irritation with significant increase of DPC and p53 wild and mutant types as pre carcinogenic effects of formaldehyde. Conclusion: The studied group in the histopathology laboratory was exposed to formaldehyde level above the exposure limits recommended by NIOSH, ACGIH and OSHA with adverse health effects in the form of increase in DPC and p53 (wild and mutant types) which are considered to play an important role in the carcinogenesis of FA.