Heat and cold often produce a similar clinical effect but different physiologic mechanisms. The purpose of this study was to compare the effects of local heat and cold therapy on joint pain, discomfort and, ROM of the arthritic knee joint. Thirty female subjects took Ice bag and hot bag with random assignment of initial therapy Subjects rated the degree of Joint pain and discomfort before and after each therapy, and then ROM was measured. The results of the study were as follows : 1. The hot bag group showed significantly lower joint pain & discomfort score than the ice bag group. ROM was increased in the hot bag group compared with subjects in the ice bag group. But there is not significant differences. 2. The ice bag group showed significantly lower joint pain score after than before therapy. But there are no significant differences in discomfort score & ROM between after & before therapy. 3. The hot bag group showed significantly lower joint pain, discomfort score after than before therapy. ROM was significantly increased after than before therapy in hot bag group. Therefore hot bag was significantly more effective than the ice bag in relieving the arthritic joint symptoms. A further study is necessary to determine the effect of local heat and cold therapy including the related variables such as preference for heat or cold.