In this prospective case controlled study 16 premenopausal women with documented irritable bowel syndrome were recruited from the gastroenterology clinic and 16 premenopausal controls without symptoms of irritable bowel syndrome were recruited from the gynaecology clinic. All women answered a standardised bowel and urinary symptom questionnaire and underwent twin channel subtracted cystometry. Women with irritable bowel syndrome also underwent oesophageal balloon distension studies for perception and pain. Oesophageal and bladder sensory thresholds were compared. Urinary frequency and urgency and the urodynamic finding of detrusor instability were significantly more common in women with irritable bowel syndrome (P < 0.05). We were unable to demonstrate a relationship between first sensation of bladder fullness and oesophageal perception or between maximum bladder capacity and oesophageal pain thresholds. These findings suggest that there is an irritable bladder in the irritable bowel syndrome and support the concept that irritable bowel syndrome is part of a generalised disorder of smooth muscle.