A group of 37 patients (24 female and 13 male) with chronic urinary retention and without demonstrable mechanical obstruction had neurophysiological measurements of their lower urinary tracts to detect any neurological abnormality which might relate to the disorder. These consisted of measurements of the electrosensitivity of the dorsal nerve of the penis/clitoris and of the urethra, measurement of the sacral reflex latencies (SRL) from dorsal nerve to urethra and to anus and between urethra and anus and EMG studies of the urethral and anal sphincters. The results suggest that female patients in particular have significant neurogenic defects in the voiding reflex arcs which find their clinical expression in detrusor underactivity with urinary retention. Plain X-rays of the renal tracts (KUB films) were also studied for the presence of spina bifida occulta. The prevalence of this defect was significantly higher than in normal controls, suggesting that in some of these patients the nerve defect might be related to a tethered cord in association with spina bifida occulta.