Purpose: The purpose of this study was to identify influencing factors of using numbers and period of complementary and alternative therapy (CAT) among chronic patients. Methods: The study employed a descriptive design. The participants were 221 chronic patients. Data were collected in a pharmacy near a general hospital from April to July, 2008. Results: Influencing factors on using number of CAT were age, numbers of disease, period of used CAT and monthly expenses on CAT (the ability to explain, 79.9%). Influencing factors on using period of CAT were the period of illness and using number of CAT (the ability to explain, 44.9%). Conclusion: The results of this study suggest that chronic patients need counseling and guides about using CAT especially for those are older and have many kinds and longer period of diseases.