Low serum high-density lipoprotein cholesterol (HDL-C) is a strong predictor of coronary heart disease (CHD). The aim of the present study was to evaluate the metabolic parameters predicting the atherosclerotic changes in asymptomatic members of low HDL-C families. We performed carotid B-mode ultrasonography with intima-media thickness (IMT) measurement for 89 asymptomatic members of Finnish low HDL-C families. The family members were categorized as affected or unaffected according to the 10th age-gender specific HDL-C percentile. In the affected group, the most marked decrease of HDL subclasses was observed for HDL2-C when compared with the unaffected (109% difference). In the partial correlation analyses, age and gender showed significant correlations with the mean IMT (for age, r=0.880, P<0.001, and for gender, r=-0.361, P=0.018). Importantly, HDL-C and HDL2-C were significantly inversely related to the mean carotid IMT, also after correction for age (for HDL-C, r=-0.186, P=0.043, for HDL2-C, r=-0.208, P=0.029, when adjusted for age). The correlation for HDL-C was significant also when adjusted for gender. In conclusion, low HDL-C is associated with increased carotid artery IMT in asymptomatic members of low HDL-C families.