Though organ transplantation has evolved in many a ways over the years, it is not without the disadvantage of causing rejections. Cyclosporin, azathioprine and corticosteroids are time tested and efficacious; however each is accompanied with its own array of disadvantages. Sirolimus is a relatively new immunosuppressant isolated from a macrolide antibiotic. It may have a beneficial role in prophylaxis of rejection as well as treatment of refractory rejection. It also has antifungal, antitumor and anti-smooth muscle proliferative roles.