We examined the effects of prostatic urethral anesthesia on cystometrography in benign prostatic hyperplasia (BPH) patients with or without neurological disorders. Although cystometrography after anesthesia showed no disappearance of involuntary detrusor contraction, it did demonstrate significant increases in first sensation volume and maximum cystometric capacity in BPH patients without neurological diseases, as well as BPH patients with a history but no physical evidence of neurological disease. Furthermore, the bladder might be augmented more efficaciously in patients with involuntary detrusor contractions. No significant differences were found in first sensation volume or maximum cystometric capacity before and after anesthesia in patients without infravesical obstruction who had documented neurological disease with physical evidence. Our results demonstrated that prostatic urethral anesthesia can be used preoperatively in patients with infravesical obstruction to discriminate whether involuntary detrusor contractions are due to infravesical obstruction or to neurological disease.