Proteasomal dysfunction plays an important role in the pathogenesis of Parkinson disease (PD). Although clinical and experimental evidence continues to accumulate indicating heat shock protein 70 (HSP70) is significant in the pathogenesis of PD, few studies have been made to investigate the role of HSP70 under the condition of proteasome dysfunction. In in vivo study, we infused lactacystin into the unilateral substantia nigra (SN) of Sprague-Dawley rats with or without preceding whole body hyperthermia (WBH). Immunohistochemical studies showed the death of dopaminergic neurons and activated microglia in the SN. Lactacystin with prior WBH increased the expression of HSP70 more than did lactacystin alone and decreased lactacystin-induced dopaminergic neuronal death in the SN. In PC12 cells, heat shock pretreatment decreased lactacystin-induced cell death. Although additional treatment of nocodazole, ammonium chloride, and 3-methyladenine augmented cell death by lactacystin, heat shock pretreated to these drugs offsets their additional toxicity. These results indicate that heat shock proteins, especially HSP70, could play an important role under the condition of proteasome dysfunction in part by fostering aggresome formation and lysosome-mediated autophagy.