Abstract：By immunohistochemistry and in situ hybridization，the localizations of heat shock protein 70 (HSP70) and HSP70 mRNA in heart，liver，lung，kidney，spleen，thymus and bursa of Fabricius of 6 h heat stressed broilers were studied. The result showed that the positive signals of HSP70 mRNA at 6 h heat stress were localized in the liver and lung，especially in the wall of vessel. The weak positive signals were seen in the myocardial cells. No significant signals were observed in spleen，thymus and bursa of Fabricius；HSP70 signals were localized in the wall of vessel of all detected tissues at 6 h heat stressed broilers. The localizations of HSP70 and HSP70 mRNA suggest that HSP70 is correlation with the cardiovascular function.
