An identifiable lumbar nerve root compression appears to cause urological dysfunction consistent with interstitial cystitis. Ten patients (9 females, 1 male) were evaluated for chronic pelvic pain. Cystoscopic and histological appearances were consistent with a diagnosis of interstitial cystitis. Magnetic resonance studies of the lower spine consistently demonstrated a lateral compression of the L5 dorsal nerve root. Decompression of the lateral foramina of L5 resulted in immediate relief of pain in 9 patients, who have been followed up for 6 months without a recurrence. Possible mechanisms involving sympathetic dystrophy of the pelvic plexus are reviewed.