Sixty cases of dyslipidemic hypertension were identified in the 1028 middle-aged, white, male twin participants in the first examination of the National Heart, Lung, and Blood Institute Twin Study (1969 to 1973). The prevalence of dyslipidemic hypertension was similar by zygosity but proband concordance was three times greater in monozygotic than dizygotic twins (0.44 [seven concordant and 18 discordant pairs] vs 0.14 [two concordant and 24 discordant pairs]), suggesting a genetic effect on the condition. Low high-density lipoprotein cholesterol level was the most common lipid abnormality in concordant pairs. Mortality from ischemic heart disease was significantly higher in individuals with dyslipidemic hypertension. Obesity and glucose intolerance were closely associated with the syndrome. Moreover, within the 18 discordant monozygotic twin pairs, the twins with dyslipidemic hypertension had gained significantly more weight as adults and were significantly heavier than their unaffected cotwins. Thus, although genetic factors may influence development of dyslipidemic hypertension, nongenetic, potentially modifiable aspects of obesity are also closely related to expression of this clinically important syndrome.