One of the cytotoxic agents most widely used and better tolerated in the management of IPF is azathioprine. Based upon limited data available and from a single small high quality randomized controlled trial (RCT), this drug appears to confer, given in conjunction with prednisone, a marginal long term survival advantage. Since this combination therapy is associated serious adverse effect, we planned to design a trial of low dose corticosteroid and azathioprine versus placebo in management of IPF, evaluating progression-free survival.