Bioavailability of microencapsulated cinnamaldehyde (CNMA) was evaluated in F344 rats. Parent chemical and its metabolite - cinnamic acid blood concentrations were measured by HPLC method after gavage dosing rat with microencapsulated cinnamaldehyde in corn oil and neat cinnamaldehyde corn oil solution at dose levels of 50, 150, 500 mg/kg. Urinary metabolite - hippuric acid was also analyzed after gavage dosing. Bioavailability of both microencapsulated CNMA and neat CNMA was found to be poor due to the severe first pass effects and rapid clearance. However, CNMA was found in systemic circulation and excreted mainly as hippuric acid was observed between microencapsulated CNMA and neat CNMA.