Mean serum lipoprotein concentrations show that increased consumption of green tea was associated with an increased serum concentration of high density lipoprotein cholesterol and a decreased concentration of serum low density and very low density lipoprotein cholesterols (table III). Serum concentrations of lipoproteins were measured by an electrophoretic separation in agarose, and the proportions of lipoprotein fractions in total lipoprotein were estimated as percentages. The association was found only in the group that drank the most green tea. A ratio of low density lipoprotein cholesterol to high density lipoprotein cholesterol, which is sometimes referred to as the atherogenic index, may also be an important index for arteriosclerosis (table III). A significant decrease in the ratio of low density lipoprotein to high density lipoprotein cholesterol was observed in the group that drank the most green tea.