Corticosteroids are currently the mainstay of therapy for active pulmonary sarcoidosis and are used to prevent relapses in many patients with stable disease. The pulmonary manifestations of sarcoidosis are heterogenous and not all patients require corticosteroid therapy. Corticosteroids often produce undesirable side effects and, therefore, other therapies that can reduce or replace corticosteroid use are being sought. As tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role in the formation of granulomata (the pathological hallmark of the disease), drugs that inhibit its production/release may prove effective in the treatment of this disease. Pentoxifylline (POF), a xanthine derivative used for many years in the treatment of peripheral vascular disease, is known to inhibit TNF-alpha release by human peripheral blood mononuclear cells and alveolar macrophages from patients with active sarcoidosis. To evaluate whether this drug is beneficial in the treatment of sarcoidosis, we propose to conduct a randomized, double-blind, placebo-controlled trial with POF in patients with pulmonary sarcoidosis on corticosteroid therapy. The primary objective of this study is to determine whether POF treatment can be beneficial as an adjunct to corticosteroid therapy in patients with pulmonary sarcoidosis. The role of TNF-alpha and other cytokines (released from alveolar macrophages) in explaining treatment responses defined by whether or not a patient improved will be assessed by testing whether the effect of treatment on the probability of improvement varies with cytokine levels.