In many catabolic conditions, including fasting, cancer, diabetes, the expression of peroxisome proliferator-activated receptor (PPAR)-γ co-activator-1α (PGC-1α) is reduced. However, there are no available data on whether the expression kinetics of PGC-1α is muscle fiber specific in response to immobilization-induced muscle atrophy. We tested the hypothesis that long-term immobilization would reduce PGC-1α expression in both oxidative (slow-twitch) and glycolytic (fast-twitch) muscles. Male C57BL/6 mice were subjected to hindlimb immobilization. Basal PGC-1α protein and mRNA in the slow-twitch soleus was markedly higher than that in the fast-twitch plantaris muscles. Unexpectedly, PGC-1α protein and mRNA expression did not decrease following immobilization in both muscles. In addition, PGC-1α protein expression positively correlated with the atrophied muscle mass only in soleus muscle at late stage of immobilization. These data suggest that PGC-1α content may be a key mediator controlling muscle mass following immobilization.