We have previously shown a negative correlation between lipid peroxide levels and prostacyclin synthesis in plasma and artery of the atherosclerotic rabbit. Here we compare the arterial lipid peroxide content, glutathione peroxidase activity, and prostacyclin and thromboxane production in response to exogenous arachidonic acid stimulation, and the cell cycle stages in normal and atherogenic diet-fed quail. Lipid peroxides were higher in arteries of the atherosclerotic quail, while glutathione peroxidase activity and prostacyclin and thromboxane production were lower than that in the control quail. The smooth muscle cell cycle distribution which was determined by flow cytometry according to DNA content showed that more than 14% of atherosclerotic arteries were mitotically active (in S + G2 + M phase), while less than 10% of control cells were active. These results suggest that there is a close relationship between lipid peroxide content, prostacyclin production and cell proliferation of the arterial wall in experimental atherosclerotic quail.