Two groups of young male macaques were fed diets which differed in physical consistency. The first group was fed a soft diet and the second group was fed a hard diet. The effect of this difference in dietary consistency on the thickness and morphology of the mandibular condylar cartilage in the superior and posterosuperior regions of the two groups was examined. Slight morphologic changes were observed in the superior region of the condylar cartilage and in the subchondral bone of the soft diet macaques. However, the thickness of the cartilage in the superior region was similar in the two groups. Significant morphologic changes were observed in the posterosuperior region in all three layers of the condylar cartilage and in the subchondral bone of the soft diet macaques. The cartilage in the posterosuperior region of the soft diet group was significantly thinner, and the subchondral bone less dense, than in the hard diet group. The results of this study showed that dietary consistency significantly affects the morphology of mandibular condylar cartilage in young macaques. It is recommended that dietary consistency be eliminated as an additional variable in future studies of mandibular and condylar responses to experimental manipulations.