The polymerase chain reaction was used to evaluate cytokine gene expression in bronchoalveolar lavage (BAL) cells and peripheral blood leukocytes in 31 human lung transplant recipients. All patients were maintained on a triple immunosuppression regimen consisting of CsA, AZA, and prednisone. Posttransplant survival ranged from 0.5 to 100.5 months (mean = 16.3 months). Cytokines IL-1α, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, TNF-β, and IFN-γ were studied. In BAL, transcripts for IL-1α, IL-7, IL-8, and TNF-β were found in over 60% of samples and those for IL-5, IL-6, and IFN-γ in 40–50%, while IL-2 and IL-4 mRNA were rarely found (10%). Transcripts for IL-4 were not found in association with pulmonary infection, suggesting that this cytokine may be useful as a discriminatory rejection marker.