Objectives:The aim of this investigation was to study the remodeling of cartilage in the mandibular condyle following disc displacement of temporomandibular joint. Methods:Forty adult Japanese white rabbits were used in this study. The right joints of 28 among the 40 rabbits were subjected to surgical operation of disc displacement. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and12 weeks after surgery respectively. The mRNA expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results:Results showed that aggrecan mRNA expression reduced in the first week after disc displacement. The expression began to recover after 4 weeks and reached to normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered in 8 weeks. Conclusions:The study concluded that the chondrocyte, reacted to the displacement of the TMJ disc, seems to alter its matrix gene expression patterns. This study was supported by Scientific Foundation of Zhejiang, P.R. China. G20030241