Human neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis have been termed "protein misfolding disorders." Upregulation of heat shock proteins that target misfolded aggregation-prone proteins has been proposed as a potential therapeutic strategy to counter neurodegenerative disorders. The heat shock protein 70 (HSP70) family is well characterized for its cytoprotective effects against cell death and has been implicated in neuroprotection by overexpression studies. HSP70 family members exhibit sequence and structural conservation. The significance of the multiplicity of HSP70 proteins is unknown. In this study, coimmunoprecipitation was employed to determine if association of HSP70 family members occurs, including Hsp70B' which is present in the human genome but not in mouse and rat. Heteromeric complexes of Hsp70B', Hsp70, and Hsc70 were detected in differentiated human SH-SY5Y neuronal cells. Hsp70B' also formed complexes with Hsp40 suggesting a common co-chaperone for HSP70 family members.