Aim To investigate the relationship between small and dense low-density lipoprotein cholesterol(sdLDLC) and the carotid atherosclerotic plaque in Chinese population.Methods The serum level of sdLDLC was examined by the automatic analyzer in 166 patients.They were all examined with the carotid colour Doppler flow imaging,and were grouped as plaque group(n=86) and no plaque group(n=80) according to the result of duplex colour Doppler flow imaging.Patients of the two groups were compared in the level of some possible risk factors including age,sex,drinking,smoking,hypertension,diabetes mellitus,and total cholesterol(TC),triglyceride(TG),low-density lipoprotein cholesterol(LDLC),high-density lipoprotein cholesterol(HDLC).Logistic regression model was applied in the screening of risk factors.Results The mean age,mean total cholesterol,mean triglyceride,incidences of hypertension and diabetes mellitus were significantly higher in patients with carotid plaques than in patients without by single-factor analysis.No significant difference of sex,drinking,smoking,the mean value of low-density lipoprotein cholesterol,high-density lipoprotein cholesterol was found between two groups.Logistic milti-factor regression analysis showed that age(OR=1.10,P<0.01),hypertension(OR=2.81,P<0.05),diabetes mellitus(OR=2.74,P<0.05) and sdLDL-C(OR=3.8,P<0.001) were involved in the regression equation statistically.Conclusions The formation of the carotid atherosclerotic plaque is the interactional result of multiplicate factor.High TG and high TC are the related risk fac-tors of carotid plaque.Age,hypertension,diabetes mellitus and sdLDLC are the possible independent risk factors for carotid plaque.