Abdominal pain/discomfort, bloating, and constipation are gastrointestinal dysmotility and sensory symptoms associated with irritable bowel syndrome (IBS). No studies have followed patients with IBS symptoms for 1 year under conditions of routine clinical practice to assess prospectively the impact of treatments on health outcomes. The objective of this ongoing, naturalistic study is to assess the long-term impact of IBS treatments on quality of life (QOL), work productivity, and resource utilization. This report describes the baseline characteristics and patterns of care of the patients enrolled in this study. Patients with physician-diagnosed IBS symptoms were enrolled from 147 physician sites across Canada between May 4, 2004, and March 31, 2005. Clinical data were collected at baseline and at the end of the 12-month follow-up (patients were followed for 1 year between May 4, 2005, and March 31, 2006). Patient-reported outcomes were collected at baseline and at months 1, 2, 6, 9, and 12. Health-related QOL, health status, and work productivity were assessed with the IBS-QOL, a 5-item EuroQol descriptive system, and Work Productivity and Activity Impairment questionnaires, respectively. A resource utilization questionnaire elicited information on physician; visits, treatments, and procedures. Baseline data are reported here. Data were obtained from 1555 patients; 85.1% (1320/1552) were women. Patients had a mean (SD) age of 45.8 (15.0) years and mean (SD) duration of IBS symptoms of 11.4 (11.5) years. Self-reported bowel patterns were predominantly constipation (41.0%, 587/1433) and constipation alternating with diarrhea (39.4%, 564/1433); 60.3% (938/1555) of subjects used > or =3 IBS treatments in the previous 4 weeks. Approximately 50% of all patients reported distress "quite a bit or "extremely" for abdominal pain, gas, bloating, and constipation. The mean overall IBS-QOL score (0-100 scale, with 0 indicating poor QOL) was 66.3; food avoidance (51.8) and health worry (59.3) were the most serious concerns. Patients reported 5.6% work absenteeism, 31.4% presenteeism, and 34.6% overall work productivity loss, equivalent to 13.8 hours lost productivity per 40-hour workweek. The baseline data from this ongoing, prospective, naturalistic study are consistent with previous findings that suggested significant use of health care resources with concomitant low QOL and decreased work productivity in patients with IBS symptoms.