This study examined the influence of the ovarian sex hormones, estrogen and progesterone, on the fiber type-specific response of the inducible 70kDa heat shock protein (Hsp70) to damaging exercise in rat soleus. Ovariectomized female rats were divided into three treatment groups (n=16 per group): sham (S), progesterone (P, 25 mg pellet) and estrogen (E, 0.25 mg pellet). Each treatment group was divided into control and exercised groups. After 8 days of sham or hormone treatment, animals ran downhill intermittently for 90 min (17 m^.min^-1, -13.5° grade) on a treadmill and soleus muscles were removed 24 h post-exercise. Hsp70 expression was assessed in whole muscle homogenates by western blotting and in individual muscle fiber types by immunohistochemical analysis of serial cross-sections of soleus samples. Comparisons between control groups showed that Hsp70 expression in soleus was increased (p<0.05) in E compared with both S and P. No difference (p>0.05) was observed between S and P. Following downhill running, Hsp70 content in soleus was increased (p<0.05) compared with control in S and P but not (p>0.05) in E. As a result, soleus Hsp70 content following downhill running was not different (p>0.05) between any of the treatment groups. Under all conditions, Hsp70 content was higher in type I versus type II fibers and the effects of both estrogen and exercise on Hsp70 expression in soleus were also more pronounced in type I versus type II fibers. These results demonstrate that: 1) estrogen regulates Hsp70 expression in skeletal muscle, increasing basal Hsp70 expression and preventing further increases in Hsp70 in response to exercise; 2) progesterone is not involved in the regulation of Hsp70 expression in skeletal muscle; and 3) the effects of estrogen and exercise on Hsp70 expression in skeletal muscle are fiber type-specific.