The functional relationship between thermotolerance and heat shock protein (HSP) expression is well described. However, the intraspecific variation in HSP70 expression and heat resistance is not fully understood. Some studies have shown a correlation between thermotolerance and HSP70 expression levels at the intraspecific level, whereas others have not, and results depend on species, developmental stage and environment. The present study extends such correlative studies to species from soil ecosystems, where we have characterized the variation in thermotolerance and HSP70 expression in 18 inbred isofemale lines of the springtail Orchesella cincta. The results show ample genetic variation among lines in heat shock resistance as well as in HSP70 protein levels and hsp70 mRNA expression. However, we did not detect any significant positive correlations between HSP70 expression and thermotolerance. These results indicate that the variation in HSP70 expression and heat resistance at the intraspecific level is dependent on species and/or ecosystem and further studies are needed to clarify this relationship. © Inter-Research 2010.