An increasing number of immunosuppressive drugs have become available for clinical use over the past few years. Respiratory medicine has not been excluded from the growing enthusiasm devoted to the use of novel immunosuppressants. New agents are currently undergoing clinical trials in pulmonary disorders characterized by acute or chronic inflammation, the "optimal" immunosuppressive strategy for the cure of interstitial lung diseases in the next decade being forthcoming. An example of this fervour may be found in this issue of the Journal: data have been provided on the effectiveness in clinical use of an inhibitor of nucleotide synthesis, leflunomide, in chronic sarcoidosis. The great choice of available agents could allow us to select the best therapeutic regimen for ail individual patient, however, this requires a comprehensive knowledge of the modes of action of the immunosuppressants we are planning to use. The present review provides an update of current understanding on the molecular mechanisms of some important immunosuppressants that are expected to play a role in the therapy of interstitial lung diseases.