Aims: To study the effect of estrogen deficiency and altered temporomandibular joint loading on the histomorphology of condylar cartilage and on the expression of types II and X collagen and matrix metalloproteinase-3 (MMP-3). Methods: Thirty-six female rats were divided into four groups: ovariectomized rats on a normal diet, nonovariectomized control rats on a normal diet, ovariectomized rats on a soft diet, and nonovariectomized control rats on a soft diet. Ovariectomy was performed at the age of 60 days. Repeated measures ANOVA was used to analyze the data. Results: The condylar cartilage in the ovariectomized normal diet group showed a significantly higher number of cells than in the nonovariectomized control rats (P .001). The proportional amount of MMP-3 expression was significantly higher in the ovariectomized rats than in the nonovariectomized control rats in both diet groups (P .001). The area covered by types II and X collagen was significantly higher in the experimental groups than in the control groups (P .01). Conclusion: Condylar cartilage is sensitive to both estrogen level and dietary loading. Keywords: estrogen, joint loading, mandibular condylar cartilage, MMP-3, type II collagen, type X collagen