The perichondrium adhering to mature cartilage is not active, but that separated from cartilage is highly chondrogenic. Cartilage formation from isolated perichondrium does not last forever, and perichondrium soon becomes inactive. What activates or inactivates the perichondrium? The authors investigated the effect of mature cartilage on the cartilage formation from perichondrial graft material. The results showed that mature cartilage attached to the perichondrium inhibited neochondrogenesis. The phenomenon that cartilage—a product of chondrogenesis—inhibits neochondrogenesis of perichondrium can be called negative feedback.