In order to investigate the time course of exercise-induced, fiber type specific heat shock protein 70 (Hsp70) expression in human skeletal muscle, ten untrained male volunteers performed single legged intermittent isometric knee extensor exercise at 60% of their maximal voluntary contraction (MVC) for 30 min. Muscle biopsies were collected from the vastus lateralis before (Pre) exercise in the rested control leg (C) and immediately following exercise (Post) in the exercised leg (E) only and on recovery day 1 (R1), 2 (R2), 3 (R3) and 6 (R6) from both legs. Western blotting showed that whole muscle Hsp70 content was unchanged (p>0.05) by exercise (Pre vs. Post), was increased (p<0.05) by ~43% at R1 and remained elevated throughout recovery. As demonstrated by immunohistochemical analysis, there were no fiber type differences (p>0.05) in basal hsp70 expression. Immediately following exercise, hsp70 expression was increased (p<0.05) in type I fibers by ~87% but was unchanged (p>0.05) in type II fibers (Pre vs. Post). At R1 and throughout recovery, hsp70 content in E but not C was increased above basal levels (p<0.05) in all fiber types but was always highest (p<0.05) in type I fibers. Glycogen depletion was observed at Post in all type II fibers but not in type I fibers suggesting that the fiber type differences in exercise-induced hsp70 expression were not related to glycogen availability. These results demonstrate that the time course of exercise-induced hsp70 expression in human skeletal muscle is fiber type specific.