The efficacy and safety of long-term administration of oxybutynin hydrochloride in patients with neurogenic bladder and unstable bladder, who complained of urinary frequency, urgency and incontinence, and whose bladder was proved to be uninhibited, reflex, and/or low compliant, were studied at the multi-center hospitals, and the following results were obtained. This study comprised 149 cases but 8 of them were excluded because of the incomplete protocol. Thus, 141 cases (104 neurogenic bladder patients, 33 unstable bladder patients and 4 others) were investigated. The daily dosage of Oxybutynin hydrochloride ranged from 1 to 18 mg, and averaged at 6.6 mg. Since a small daily dosage of 3 mg was administered in 32 cases to examine the minimum effective dosage of the drug, the low average dosage possibly resulted. The clinical optimal dosage seemed to be more than 6.6 mg. The average period of administration in all cases was 161.7 days (1-336 days), and the drug was discontinued in 46 cases (33.6%) on average 62.1 days (1-141 days). The rate of global improvement by this drug estimated at the time of completion was found to be 65.6% with excellent and good and 87.8% with excellent, good and fair. The efficacy of this drug was stable and not decreased during the long-term test period. As to the objective findings studied before, during and after the drug administration, cystometric bladder capacity was significantly increased both first desire to void and the total capacity. Voided volume and residual urine were also increased, but there was no change in the rate of residual urine. Side effects were observed in 37 (26.2%) of 141 cases, and mainly gastrointestinal signs such as dry mouth and constipation. Urological signs such as dysuria and urinary retention were experienced in 8 cases. Regarding the findings of laboratory tests, there were no abnormality except for small changes of some items in normal range. Six children who were younger than 15 years old were subjected to this study. The results of evaluation were similar to those obtained on adults and no side effects were observed. From these findings, oxybutynin hydrochloride is considered an effective and useful drug in patients suffering from neurogenic bladder and unstable bladder with over active bladder condition.