We examined symptom frequency, duration, andseverity, as well as episode patterns, in 122 adultpatients with irritable bowel syndrome in a 12-weekstudy conducted in the United States, the UnitedKingdom, and The Netherlands. Patients used aninteractive telephone data entry system daily to reportsymptoms. Data from 59 of the patients meeting inclusioncriteria are presented, the remainder having beenexcluded for failing to complete at least 70 days ofsymptom reporting. The majority of patients experiencedat least one symptom on over 50% of the reported days;however, individual symptoms were reported on less than 50% of the days, indicating that symptomssometimes occurred sequentially rather than alwayssimultaneously. On average, patients reportedpain/discomfort on 33% of days, bloating on 28% of thedays, altered stool form or stool passage on 25% and18% of the days, respectively, and mucus on 7% of thedays. The duration of symptoms was relatively short,with pain/discomfort and bloating lasting the longest, an average of five days each per episode. Allsymptoms but one (mucus) were moderately severe on themajority of reported days. Patients experienced an“episode” (defined as a period of days withsymptoms bounded by one or more symptom-free days) on anaverage of 12.4 times during the study, but the durationof these episodes varied greatly among patients. Theseresults further establish the chronic nature of irritable bowel syndrome and the burden thatthis condition imposes on patients.