Familial hyperlipidemia has received little attention as a possible cause of stroke in young patients. Some recent studies have demonstrated that lipoprotein (a) is a key factor for atherogenesis in familial hypercholesterolemia. Hypogonadism may also contribute to the elevation of serum lipids, but their influence as a risk factor for stroke is still less understood. A 34-year-old patient with heterozygous familial hypercholesterolemia presented with a left pure motor hemiparesis secondary to a right striatocapsular infarction. Arteriography showed atherosclerotic lesions in both internal carotid arteries. High levels of cholesterol, cLDL, apo B, and lipoprotein (a) were found. Clinical signs of hypogonadism were present and the karyotype led to the diagnosis of Klinefelter's syndrome (47,XXY). The early clinical course was excellent, and the levels of serum lipids were normalized with diet, lipid-lowering drugs and androgens. The importance of hyperlipidemia as a risk factor for stroke in the young, specially when it occurs in the context of familial hypercholesterolemia with elevated lipoprotein (a) levels, as well as the possible contribution of hypogonadism to the development of accelerated atherosclerosis in young patients, are discussed upon.