Weanling rats were offered food ad libitum, or fasted for 18 h, or fasted and refed for times ranging from 5 to 30 min. Five protein kinase C (PKC) isoforms (α, ε, ζ, and μ) were detected in the hindlimb muscles by Western immunoblotting. PKC forms ε and were abundant in plantaris, but not in soleus muscle, and no difference in localization was detected between fed rats and those fasted for 18 h. PKC forms α and μ were affected by fasting and refeeding. PKC-μ was found only in the cytosolic fraction of the plantaris muscle of the fasted animal, but in the fully-fed animals it was also associated with the membrane fraction. The pattern of localization observed in the fully-fed state was restored in the fasted rats by 20 min refeeding. In contrast, PKC-α was not detected in the cytosolic fraction of the plantaris in fasted animals but rapidly reappeared there on refeeding, being restored to 20 % and 80 % of the fed value within 5 and 30 min of refeeding respectively. The timing of these changes was correlated with the increase in serum insulin concentration, which was significantly elevated above the fasted value by 5 min and at subsequent times. These data suggest a possible role for PKC isoforms α and μ in the metabolic changes that occur in skeletal muscle on transition between the fasted and the fed state.