Heme oxygenase is an inducible rate-limiting enzyme for hemedegradation in mammalian cells. In this study the expression of human HO-1 gene in human atherosclerosed arteries was examined.Human HO-1 mRNA were studied in 34 tissue samples. Fifteen human arterial samples diagnosed histopathologically as advanced atherosclerosis and 5 human arterial tissue samples diagnosed histopathologically as early atherosclerosis and 14 samples from traumatic injured arteries as non-atherosclerotic control. We use RT-PCR for detection of human HO-1 mRNA.The results showed positive HO-1 mRNA expression only in advanced atherosclerotic samples.This suggesting that HO-1 has a role as a protective enzyme, manifested variously in different vascular cells, modulating the severity and progression of atherosclerosis.