Irritable bowel syndrome (IBS) has been reported in 10% to 22% of adults. The authors compared patients seeking treatment for dysthymia (N = 59) in an outpatient setting to an age- and sex-matched comparison group of patients (N = 54) seeking treatment in a general physician's office for other medical illnesses. The comparison group did not have any Axis I disorders. IBS was diagnosed by using the criteria established by Drossman and colleagues. Of the patients screened, 59.32% of the patients with dysthymia met criteria for IBS in contrast to 1.85% of the comparison group (P < 0.000005). IBS is extremely prevalent in patients seeking treatment for dysthymia and is often undiagnosed and untreated.