 Background, cyrolimus is immunosuppressive drug used to prevent rejection in kidney transplantation. Pulmonary problems are one of the serious complications which may be seen after administration of this drug and it is believed that it could be life-threatening. Case presentation, here in this paper we presented a 49 years old man with bronchiolitis obliterans organizing pneumonia, BOOP, induced by chronic use of cyrolimus. The disease was diagnosed and successfully treated. Conclusions, cyrolimus uses after kidney transplantation may lead to lung complications, especially BOOP, and the prompt diagnosis would allow earlier treatment. This article was authored by Bezzat Ainalahi, Jaffer Aslani, Mirdad Tagapur, and others.