Temperature dependence of T1 of tissue water in the porcine knee joint cartilage in vitro was examined at 9.4T in comparison with that of the water proton resonance frequency. The absolute value of T1 at each temperature between room temperature and 60oC was reproducible. Hysteresis was negligible during heating and cooling processes. The correlation coefficient with temperature was higher than 0.998, and hence that with water proton chemical shift was also high (>= 0.996). The temperature coefficient was 1.28%/oC at 30oC for heating and 1.24%/oC for cooling. These results suggested that T1 is a favorable index for thermometry of the knee joint cartilage under thermal therapies.