Purpose: The purpose of the study was to compare the effects of Tai Chi exercise program on arthritic pain, difficulties in performing activities of daily living, and fear of falling in women with osteoarthritis (OA) and rheumatoid arthritis (RA). Method: A quasi-experimental design with two intervention groups was used. According to the inclusion criteria, 35 women with OA and 22 with RA were recruited and participated in the Tai Chi for arthritis program for 12 weeks. In 12 weeks, 21 in the OA group and 15 in the RA group completed both pretest and posttest measures. Outcome variables consisted of pain, difficulties in performing activities of daily living, and fear of falling for both groups. Results: The women with OA (64 years) were significantly older and perceived better health than those with RA (49 years) with more than 6 years of diagnosis. The pain scores and the performance of activities of daily living were significantly improved in the OA group at the completion of 12 week Tai Chi exercise, but RA group decreased pain only. The improvements in pain and activities of daily living were significantly more in women with OA than those with RA. No significant changes were found in fear of falling for both groups. Conclusion: The 12 week Tai Chi exercise was more effective on pain and activities of daily living for women with OA than those with RA. Considering that the women with RA perceived more pain and had limited activities of daily living, Tai Chi exercise should be applied slowly and gradually for longer period of time than those with OA.