In a regional blood transfusion centre, we observed 45 episodes of hyperlipidemic plasma among the 45,000 units produced from 12,000 unpaid volunteer blood donors during a two year period. Analysis of fasting serum cholesterol and serum triglycerides showed that 26 of the 45 were raised in either one or both of the values. Dietary instructions were given, in most cases through their general practitioners, who were informed of the results. Control of serum lipids taken in average 9.5 weeks later by the general practitioner showed a remarkable decrease in triglyceride and a slight decrease in serum cholesterol. Among the 26 we found one case of non insulin dependent diabetes mellitus, three possible and three chronic alcohol abusers. Based on these findings, fasting serum cholesterol and serum triglyceride are now analysed in donors, who repeatedly show hyperlipemic plasma.