To study the phenomenon of chondrocyte hypertrophy, rat or mouse isolated epiphyseal chondrocytes were transplanted into the kidney, spleen or liver for 7 days. Each transplant had its own control transplanted intramuscularly. Rat chondrocytes were also placed on a chorioallantoic membrane of chick embryos, incubated for 11 days and transferred for the next 11 days either onto another chorioallantoic membrane or into rat muscle. The surface area of largest lacunae cross-sections in cartilage produced by transplants was measured as an indicator of chondrocyte hypertrophy. In cartilage from the chorioallantoic membrane chondrocytes remained small but hypertrophied after transfer into a muscle. Lacunae in seven-day-old cartilage nodules in the liver were considerably larger than in muscle, kidney or spleen. After 7 days matrix calcification was observed only in liver transplants. Thus, liver environment, stimulated chondrocyte hypertrophy. Taken together these results suggest that chondrocytes are unable to hypertrophy spontaneously and that the rate of hypertrophy is subjected to regulation by extra-cartilaginous factor(s).