OBJECTIVES: Tegaserod appears to be safe and effective for treating constipation-predominant irritable bowel syndrome (IBS-C). The present study evaluates whether tegaserod is cost-effective compared to usual care, which consists of education, reassurance, suggestions on lifestyle and diet, and discussion about psychosocial issues. METHODS: The study employed a Markov-cycle tree to evaluate the medical and economic outcomes of repeated treatment with tegaserod compared to usual care in a hypothetical cohort of 1000 female patients ages 18-65 years. Probability and utility estimates were obtained from clinical trials; costs were derived from published fee schedules and other sources. Using a societal perspective over a 60-week time horizon, treatment of tegaserod was compared to usual care based on costs, quality-adjusted life-years (QALYs), and incremental cost-utility ratio (ICUR). One-way sensitivity analyses were conducted to assess the effect of varying baseline estimates within plausible ranges on ICUR, and a probabilistic sensitivity analysis in which parameters were varied simultaneously over predefined probability distributions was conducted. RESULTS: Although the cost of tegaserod treatment was higher than that of usual care ($1,070,761 vs. $173,000), the outcomes of tegaserod treatment were also better than those of usual care (834 QALYs vs. 806 QALYs). The resulting incremental cost-utility ratio was $32,113/QALY. The probability that tegaserod remains cost-effective within the generally accepted $50,000 per QALY decision threshold is more than 80%. One-way sensitivity analyses demonstrate that the results are most sensitive to the costs of tegaserod and the utilities associated with treated and untreated IBS. In probabilistic sensitivity analyses, the costs of tegaserod accounted for 77% of variation in the ICUR. CONCLUSIONS: For treatment of IBS-C in females, tegaserod is cost-effective compared to usual care.