Idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) is a disorder with a very poor prognosis for patients who do not respond to therapy with corticosteroids alone or in combination with immunosuppressive drugs, e.g. cyclophosphamide or azathioprine. For patients with end-stage disease, lung transplantation remains the only possibility for long-term survival. We describe a patient who received a left single lung transplant for end-stage desquamative interstitial pneumonitis. One year later, the patient again began complaining of exertional dyspnoea and a gradual decline in the transfer factor of the lung for carbon monoxide (TL,CO) was apparent. A recurrence of the primary disease in the transplanted lung was suspected on transbronchial biopsies. During treatment with high doses of steroids, a Pneumocystis carinii pneumonia developed, which was treated with co-trimoxazole. The patient completely recovered and, after a period of over 2 yrs, remained in an excellent condition, after which time he was lost from follow-up.