The histochemistry of the articular cartilage of the pterygoid-parasphenoid articulation has been studied and compared with adventitious and primary cartilage. Unlike adventitious cartilage the articular cartilage does not calcify and does not contain lipid or alkaline phosphatase. By the use of in vitro culture of the articulation initiation of articular chondrogenesis and joint cavitation has been prevented. It is postulated that a mechanical factor is the evocater of the articular cartilage.