Procedures and mechanisms of bamboo cell wall digestion in the giant panda were studied, in which several indirect methods were combined to avoid spoiling the intactness of the experimental animal. Examinations with surface scanning electron microscopy showed less extensive degradation of bamboo leaf tissues in panda feces than in the residue of sheep rumen digestion. Amounts of remaining fermentable organic matter, as estimated from the amount of volatile fatty acid produced during rumen fermentation in vitro, were much higher in the panda feces than in the residue of sheep rumen digestion. Incubation of fresh excreted panda feces for 12 hr at 37°C simulating extension of the digestion time caused no further progress of digestion. In vitro digestion with gastric juice of the panda showed some decrease of substrate cellulose at lower pH without corresponding reducing sugar production, although neither apparent cellulose digestion nor reducing sugar production was found with pressed fluid of the panda feces. Results showed that no bamboo cell wall digestion occurred with microbes or enzymes in the digestive tract of the panda.