To evaluate the sex hormone status of young male patients with irritable bowel syndrome (IBS) and to investigate whether there were any differences in bowel symptoms related to the hormone levels. Thirty-eight young male patients with IBS were compared with 20 healthy young men. Details of symptoms were collected by a structured questionnaire. Each subject underwent a blood test and colonoscopy. The blood test included serum testosterone, free testosterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone and luteinizing hormone. Based on the questionnaire, patients were classified as having diarrhea-predominant IBS (IBS-D) or constipation-predominant IBS (IBS-C). Among the 38 patients with IBS, 24 had IBS-D and 14 had IBS-C. The patients had higher levels of testosterone and SHBG than did the controls (p= 0.04 and p= 0.03, respectively). However, there was no significant difference between the IBS-D and IBS-C group with regard to the testosterone and SHBG levels (p> 0.05). There was also no difference in the duration and severity of symptoms between these 2 groups (p> 0.05). Sex hormone status in young men differ from those in older men and may play an important role in the pathophysiology of IBS, regardless of the dominant symptom type.