Rapamycin/sirolimus (SR), trade named Rapammune (Wyeth-Ayerst, Sydney, Australia), is a potent immunosuppressive drug associated with myelosuppression, hypertension, hyperlipidemia, and infection. Rapamycin/sirolimus-induced pneumonitis has been described previously in renal transplant recipients, and this report describes a stable heart-lung transplant recipient who developed a pulmonary infiltrate that reversed after ceasing SR therapy. We believe that immunosuppression-induced pneumonitis in a lung allograft is a serious dilemma for lung transplant physicians