The effect of various muscle conditions on anserine and carnosine contents suggests that these peptides have some physiological role in muscular functions. These conditions are: 1) Although the anserine content in rat gastrocnemius muscle was not changed by ischiamic denervation, the carnosine content was significantly decreased. Carnosinase activity in the denerved gastrocnemius muscle was two times stronger than that of intact gastrocnemius muscle. 2) Carnosine content in rat gastrocnemius muscle was also decreased by forced swimming exercise. 3) Neither anserine nor carnosine was detected in sarcoma and granuloma. 4) In rabbit, anserine and carnosine contents in white muscle fibers were 12-17 and 1-2 mumole/g of wet tissue and were approximately 10 and 2 times more than those in red muscle fibers, respectively.