Background: Increased levels of tumour markers: carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC-Ag), Alpha feto protein (AFP), and neuron-specific enolase (NSE) may indicate the onset of the carcinogenic process. The aminotransferases, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), are the most commonly measured enzymes that detect hepatocellular injury. Formaldehyde has an important application as a disinfectant and preservative, reason why relevant workplace exposure may also occur in pathology and anatomy laboratories and in mortuaries. Urinary thioethers are excretion products resulting from a series of metabolic reactions which involve oxidation of lipophilic chemicals to water-soluble compounds. Objective: The aim of the present study was to evaluate of the hazardous effects of occupational exposure to formaledehyde among lab technicians through measuring liver enzymes, hepatic tumor marker (AFP, CEA) and levels of urinary thioether as indicator of exposure to  Carcinogenic compounds. Method: the study was conducted on thirty male workers employed in medical pathology and anatomy teaching laboratories. Thirty subjects were recruited as a control group matched for age, sex and socio-economic status. Results: the resultsrevealed a high significant increase in the levels of urinary thioethers in exposed workers than those of control group and high significant elevation in the levels of tumors markers (CEA and AFP) in exposed workers in comparison with control group. Moreover, a significant increase in the levels of liver functions (AST and ALT) was observed in formaldehyde exposed workers. Conclusion: Present data indicate that formaldehyde exposed workers exhibit an increase in tumor markers levels and additionally increase in the levels of urinary thioethers. Safety Preventive measures should be applied for reduction of the formaldehyde vapors in these laboratories.