The conventional approach for management of retroperitoneal fibrosis (RF), an inflammatory process of retroperitoneal fibro-adipose tissue, leading to the compression and obstruction of the ureters and other adjacent organs is ureterolysis with omental wrapping, and an effective alternative to surgery is immunosupressive medication such as oral corticosteroids. Sairei-to (TJ-114) is a traditional herbal medicine used for the treatment of RF in Japan. It has both anti-inflammatory and anti-allergic effects. Here we report two cases of RF successfully treated with Sairei-to. One case was idiopathic and the other was caused by artificial graft-induced vasculitis. Both cases were treated with Sairei-to following the decompression of uremia by precutaneous nephrostomy or indwelling ureteral stents. There was hardly any ureteral obstruction three months after the administration of Sairei-to. They have been doing well for 12 and 26 months. Sairei-to rarely causes side effects such as immunodeficiency, gastro-duodenal ulcer and osteoporosis that often accompany long-term administration of corticosteroids. Sairei-to is a safe and effective medicine for the treatment of RF. We therefore recommend Sairei-to as an alternative for corticosteroid therapy.