The results of blood-lipid screening of 200 39--49-year-old participants with incidentally diagnosed corneal arcus from the Copenhagen City Heart Study are reported. A large sample of study-participants of the same age-group without arcus served as controls. In general, the arcus-group had higher se.-cholesterol than the control-group (P less than 0.01 in males and less than 0.02 in females). The se.-triglycerides in the two groups did not differ. A trend towards positive correlation between arcus-intensity and cholesterol-level was demonstrated by non-parametrical statistics. By use of the same statistics, an association between lipids and arcus-localisation was searched out. Dense arcus in the nasal/lower limbal regions occurred together with hypercholesterolemia more often than did a marked upper/outer arcus. Consequently, based on the present investigation, se.-cholesterol-screening of middle-aged persons with marked lower/nasal arcus seems justified, since hypercholesterolemia might will be an underlying cause. Finally, the importance of diagnosing and treating hypercholesterolemia is briefly discussed.