Formaldehyde (FA) is a chemical, traditionally used in pathology andanatomy laboratories as a tissue preservative. Many studies clearly indicatedthat FA can induce genotoxic effects in peripheral lymphocytes and isclassified by the International Agency for Research on Cancer (IARC) ascarcinogenic in humans and experimental animals.Objective: The purpose of this study is to evaluate the possible health effectsof formaldehyde among medical personnels in the HistopathologyLaboratory by evaluating its genotoxic and precarcinogenic effects.Subjects and methods: This study was carried out at Cairo UniversityHospitals and comprising 59 employees, 30 occupationally exposed toformaldehyde in histopathology laboratory and 29 with nearly the same age,gender and socioeconomic status as the exposed group and with no historyof occupational exposure to formaldehyde. All employees (exposed andcontrol) were subjected to laboratory investigations including DNA proteincrosslink (DPC), sister chromatid exchange (SCE) and micronucleus (Mn)frequency, p53 mutant and wild types measurements in peripheral bloodlymphocytes.Results: This study shows an increase in Deoxyribonucleic acid (DNA)protein crosslinks (DPC) as a primary genotoxic effects of formaldehyde aswell as increase in sister chromatid exchange (SCE) and micronucleus (Mn)frequency as other genotoxicity biomarkers. There is also increase in p53wild and mutant types which are considered the precarcinogenic effects.Conclusion: The formaldehyde level is above the recommended level byNational Institute of Occupational Safety and Health (NIOSH), American Conference of Governmental Industrial Hygienists (ACGIH) andOccupational Safety and Health Administration (OSHA). This study showsan increase in DPC, SCE and Mn as genotoxicity biomarkers as well asincrease in p53 both wild and mutant types which are considered asprecarcinogenic in cancer. Both genotoxicity biomarkers and p53 playimportant roles in the carcinogenesis of FA.