In vivo and in vitro culture of rat tumor chondrocytes is a good culture model for physiologic, pathologic and biochemical studies of tumor chondrocytes. Human tumor chondrocyte culture is another method, but it is difficult to maintain a cell line and in vivo culture. So called, Swarm Rat Chondrosarcoma, which wss developed spontaneously in a Spra-gue-Dawley rat and maintained by Dr. R. Swarm, can be cultured in vivo and in vitro at the same time. It is easy to maintain Swarm Rat Chondrosarcoma and is said that there are nearly no notable changes in cellular characteristics during consecutive cultures. In this study, in order to establish the basic culture method of rat tumor chondrocytes, the inoculated tumor mass were studied with swarm rat chondrosarcoma cell line which had been preserved at Orthopedic Research Laboratory of the Msssachusetts General Hospital. In vivo culture, injection of digested 1×10(6) cells, 1×10(7) cells and direct inoculation of tumor of mass were done at each 10 Sprague-Dawley rats group and examination was done at postinoculation 2, 3, 4, 5, 6, 7 and 8 weeks. In vitro culture, 1×10(6)/ml, 2×10(6)/ml and 4×10(6)/ml concentration cell suspensions were plated at 96-well-plate and observed at 2, 3, 4 and S days with inverted microscope. The results of this study are as follows. 1. In vivo culture, the best result was observed at direct inoculation of tumor fragments among 1×10(6) cells, 1×10(7) cells and direct tumor fragments inoculation. 2. The ideal time of obtaining tumor mass growing in rsts is between 4 to 6 weeks after inoculation. 3. In vitro culture, the proper cell density in 96-well-plate was 1 x 10(6)/ml among 1×10(6)/ml, 2×10(6)/ml snd 4 × 10(6)/ml