This review of the significance of ceroid within the atherosclerotic intima proposes that the macrophages have a central role to play in its production. Ceroid is more than merely an "age pigment." It marks the site of previous oxidative events, possibly including the release of biologically active or toxic, soluble oxidized molecules. This being so, this activity of macrophages may have a significant role in the progression of the lesions. The interactions of macrophages and oxidizable unsaturated lipids therefore merit further investigation.