Background : Xanthoma is an interesting disease entity that often indicates underlying lipid abnor malities. but, clinical studies about hyperlipopropeinemia in xanthoma were rarely present. Objective : The purpose of this study is to observe the clinical and histopathologic features in x anthoma and to evaluate relationship between hyperlipoproteinemia and underlying xanthoma. Method : 57 cases of xanthoma were analyzed. In 35 cases, blood lipids including triglyceride, cholesterol and high density lipoprotein were analyzed. And clinical characterics of xanthoma and hyperlipoproteinemia were evaluated in 10 cases of our hyperlipoproteinemic patients confirmed by electrophoresis. Results : 1. The ratio between male and female was 1:1.45 in xanthoma excluding xanthelasma and was 1:1.86 in xanthelasma only. The mean age of each group was 28 years and 52 years. 2. The incidence of each type, in descending order, was xanthelasma(35%), tuberous xanthoma(20%), eruptive xanthoma(14%), plane xanthoma(7%), tendinous xanthoma(2%), and unclassified(17.5%). 3. The associated diseases, in descending order, were diabetes mellitus(9/15), fatty liver(2/15) etc. Among these, diabetes mellitus was the most common associated disease in hyperlipoproteinemia group(6/10). 4. Histopathological features in 26 cases revealed lipid-laden foamy cells in all cases, and foreign body giant cells, fibrosis, cholesterol clefts in some cases. 5. Among 35 cases, the rate of abnormal lipid profiles, in descending order, was xanthelasma(63.3%), eruptive xanthoma(62.5%), and tuberous xanthoma(38%). 6. The frequent types of hyperlipoproteinemia in our cases, in descending order, are Ⅴ(5/10), type Ⅱa(3/10), Ⅳ(2/10). 7. In previously reported hyperlipoproteinemia with xanthoma patients, the frequent types of xanthoma, are tuberous xanthoma(12/30), plane xanthoma(8/30), eruptive xanthoma(6/30), mixed type(2/30), and xanthelasma(1/30), and the frequent types of hyperlipoproteinemia in descending order are Ⅱa(9/30), Ⅳ(8/30), Ⅴ(4/30), Ⅱb(3/30), Ⅲ(3/30), unclassified(2/30), and Ⅰ(1/30). Conclusion : The most common type of hyperlipoproteinemia in our cases and ]iteratures is type Ⅱa. but, recently type Ⅳ and type Ⅴ are increasing and are associated with increased incidence of diabetes. The incidence of abnormal lipid profiles in xanthelasma is 63.3% and routine lipid profile study will be needed in the evaluation of xanthoma including xanthelasma. (Korean J Dermatol 2003;41(11) : 1433∼1439)