Abstract: Objective To study the correlation of hlamydiapneumoniacl(CPn)infection and a thero sclerosis.Methods Eight-week-old SPF male C57BL/6J mice were divided randomly into 4 groups:normal group(groupⅣ),C Pn-infected group(groupⅣ),high-fat group(groupⅡ)and high fat-infected group(groupⅢ).A week after being fed with cholesterol-supplem ented diet,groupⅡ and groupⅣ were inoculated with CPn at 0.5-1×10⁷ IFU perino culation.Each mouse of the two groups was inoculated once weekly for 3 consecutive weeks.Eighteen weeks after the first inoculation,all the mice were sacrificed and the related index were examined.Results Compared with groupⅠ,the differences of serum TNF-level in groupⅡ,groupⅢ and groupⅣ were of statistical significance(7.196±0 436,4.236±0.408,8.881±0.529 vs 1.528±0.389,P<0.01)and so as for serum IL-10 and sVCAM-1 level in groupⅣ(541.30±99.97 vs 117.20±45.40,8.176±0.489 vs 6.183±0.394,respectively,P<0.01);serum IL-6,sICAM-1 and sE-selectin level in groupⅡ and groupⅣ(89.70±9.35,123.30±8.97 vs 65.50±8.54;and 4.545±1.232,6.131±1.083 vs 2.418±0.694;and 297.10±93.72,405.50±45.59 vs 193.10±24.71,respectively,P<0.01).Compared with groupⅣ,serum TNF-,IL-6,IL-10,sICAM-1,sVCAM-1 and sE-selectin in groupⅡ and groupⅢ were significant different (7.196±0.436,4.236±0.408 vs 8.881±0.529,89.70±9.35,77.20±6.97 vs 123.30±8.97,249.20±124.84,191.80 ±72.37 vs 541.30±99.97,4.545±1.232,2.966±1.511 vs 6.131±1.083;6.672±0.421,6.714±0.944 vs 8.176± 0.489;297.10±93.72,234.30±45.68 vs 405.50±45.59,P<0.01),respectively.Compared with groupⅠ,the difference of end othelial cells injury degree in all other three groups was of statistically significance(all P<0.01).Compared with groupⅣ,the differences of end othelial cells in jury degree in groupⅡ was of statistical significance(P<0.01).Compared with groupⅠ,the difference of plague area index in groupⅢ and groupⅣ was of statistical significance(13.90±6.58,15.53±7.20 vs 0,all P<0.01).As for re sponsibility to acetylcholine relaxing blood vessel,the difference between groupⅢ and groupⅠ was statistical significant(46.13±5.76 vs 66.85±6.37,P<0.01);the difference bewteen groupⅣ and other three groups had statistical significance(34.62±5.52 vs 66.85±6.37,62.33±5.81,46.13±5.76,P<0.01).Conclusion CPn infection could intensify the effect of high-fat diet on inducing a therosclerosis.