OBJECTIVES: To understand resource utilization and costs associated with referrals and testing for patients with irritable bowel syndrome with constipation (IBS-C) based on treatment response. METHODS: A web-based survey was conducted for a sample of primary care physicians (PCPs) and gastroenterologists (GEs) across different US regions.  The survey captured data on referral patterns (to/from gastroenterologists), test/procedure ordering, and follow-up physician visits for typical patients who did and did not achieve a satisfactory relief of symptoms to a recent treatment for IBS-C (“response”).  Survey items included questions regarding the proportion of patients who would receive tests/procedures and follow-up physician visits.  Healthcare costs were estimated by applying associated unit costs (derived from the 2012 Medicare physician payment schedule) to the corresponding utilization.  All patients were assumed to begin treatment with PCPs.  The cost of treatment failure was defined as the cost difference between physician-deemed non-responders and responders, incorporating both PCP work-up costs and the costs of referrals to GEs.    RESULTS:  Twenty PCPs and 21 GEs completed the survey. Mean monthly number of adults treated by the physicians was 61.  Most non-responders (median: 80%; mean: 72%) would be referred to a GE by PCPs.  Non-responders would be more likely to receive a test/procedure compared to responders (median: 75 vs. 0% for PCPs; 50 vs. 0% for GEs; mean: 65 vs. 10% for PCPs; 56 vs. 33% for GEs).  Thyroid function tests, complete blood count, and colonoscopy were the most common tests/procedures that would be ordered, by both PCPs and GEs.  The median (mean) expected cost of treatment failure was estimated to be $825 ($613). CONCLUSIONS: Not responding to treatment may result in referral to a specialist and/or additional testing and procedures, which may lead to higher health care resource use and costs among patients with IBS-C, a finding of potential interest to payers.