In this experiment the effect of dietary cholesterol in a linoleic acid-rich diet on serum cholesterol was tested. In a cross-over design 41 young healthy students received a linoleic acid-rich diet for 4 weeks at two levels of dietary cholesterol. The diet contained 14 to 15 energy% linoleic acid. The high cholesterol diet was obtained by adding two egg yolks a day to the rations. Supplementation of the linoleic acid-rich diet with the egg yolk cholesterol caused a significant rise of serum cholesterol of about 11 mg/100 ml (0.29 mmole/liter). The dietary cholesterol did not influence serum triglyceride levels. The influence on serum cholesterol was much less than expected, based on several predictive formulas. It is concluded that the presence of a high content of linoleic acid in the diet reduces the effect of dietary cholesterol on serum cholesterol if the cholesterol is provided as egg yolk.