In spinal cord injury, the detrusor pressure, as a parameter of urinary bladder dysfunction, is related to incontinence and renal complications. In order to determine the intraindividual variation of maximum pressure and duration of detrusor contractions, in patients with a spinal reflex bladder, the detrusor pressure was registered during 24 hours of physiological filling in 16 patients. Between the bladder contractions the detrusor pressure was low in all patients, indicating high bladder complicance. During contractions the maximum detrusor pressure and its duration varied both inter- and intraindividually. In individual patients, however, mean values during the initial 12 hours correlated with mean values during the final 12 hours. Thus, mean values of a series of contractions appear to be characteristic of each patient and useful in describing the voiding pressure in spinal reflex bladder.