Background: Constipation is a common gastrointestinal problem worldwide. The aim of this study was to determine the frequency of use and prescriptive patterns of Chinese herbal medicine (CHM) in treating constipation by analyzing the claims data of traditional Chinese medicine (TCM) from the National Health Insurance (NHI) in Taiwan. Methods: The computerized claims dataset of the TCM office visits and the corresponding prescription files in 2004 compiled by the NHI Research Institute in Taiwan were linked and processed. Visit files with the single diagnostic coding of constipation (ICD-9-CM code 564.0) were extracted to analyze the frequency and pattern of corresponding CHM prescriptions. The association rule was applied to analyze the co-prescription of CHM in treating constipation. Results: There were 152,564 subjects who visited TCM clinics only for constipation in Taiwan during 2004 and received a total of 387,268 CHM prescriptions. Subjects between 20 and 29 years of age comprised the largest number of those treated (25.5%). Female subjects used CHM for constipation more frequently than male subjects (female:male = 3.31:1). There was an average of 4.6 items of single Chinese herbs or formula in a single prescription for constipation. Ma-zi-renwan was the most commonly prescribed herbal formula, while Da-huang (Rheum palmatum) was the most commonly used single Chinese herb. According to the association rule, the most common prescribed pattern of 2-drug combination of CHM for treating constipation was Ban-xia-xie-xin-tang plus Ma-zi-ren-wan, while the 3-drug combination of CHM was Fang-feng-tong-sheng-san, Rheum palmatum and Ma-zi-ren-wan. Conclusion: This study showed the pattern of single Chinese herbs or herbal formulae used in treating constipation in Taiwan. Further clinical trials are needed to evaluate the efficacy and safety of these CHMs in treating constipation.