Degradation of purine nucleotides was evaluated in different types of rat skeletal muscle during ischemic and non-ischemic contraction. Extensor digitorum longus (EDL, fast) and soleus (slow) muscles were stimulated electrically via the sciatic nerve (5 Hz, 10 min). Under non-ischemic condition, the concentrations of IMP, inosine, adenosine, and hypoxanthine increased in EDL muscles but not in soleus muscles during stimulation. Under ischemic condition, these metabolites increased in both EDL and soleus muscles and the changes in concentrations of IMP and inosine were greater in ischemic EDL muscles. The increase in inosine had a strong positive correlation with that in IMP in ischemic EDL and soleus muscles, but the ratio, Δinosine/ΔIMP was smaller in EDL muscles. The increase in adenosine under ischemic condition was not significantly different between the two muscles. These findings suggest that ischemia enhances overall degradation of purine nucleotides in contracting fast and slow muscles, and that although the degradation of adenine nucleotides to IMP is greater in fast muscles than in slow muscles, the relative degradation rate of IMP to inosine with respect to the intramuscular IMP concentration is rather smaller in fast muscles.