This paper reviews the available evidence concerning the atherogenic p
otential of carbon monoxide. The evidence comes from two different typ
es of studies - epidemiology studies on populations of humans chronica
lly exposed to carbon monoxide, and animal studies conducted under con
ditions of controlled exposure to carbon monoxide. Data from both epid
emiology and animal studies suggest that carbon monoxide is not athero
genic. Therefore, the increased levels of atherosclerosis associated w
ith smoking as reported in epidemiology studies of human smokers proba
bly cannot be attributed to CO exposure.