Background : Corticosteroids in combination with cytotoxic drugs are the mainstays of therapy for idiopathic pulmonary fibrosis (IPF). However, there has been no regimen showing any survival benefit. The aim of this study was to describe a short-term clinical experience on interferon gamma-1b (IFN-${gamma}1b$) therapy for IPF, as an antifibrotic agent. Methods : Medical records of 27 patients who were treated with IFN-${gamma}1b$ (2 million IU, 3 times a week, subcutaneous injection) were retrospectively reviewed. Treatment response was assessed using ATS/ERS criteria in 17 patients who received IFN-${gamma}1b$ for more than 6 months. In addition, we compared the efficacy of IFN-${gamma}1b$ therapy with that of cyclophosphamide${pm}$prednisolone therapy (n=26). Results : The median age of IFN-${gamma}$ treated group (M:F=19:8) was 59 years (44-74 years). Compared to the patients who showed a stable response at 6 months (n=12), the deteriorated group (n=5) had worse baseline lung function (FVC, $55.4{pm}11.3%$ vs. $70.7{pm}10.9%$, p=0.019; DLco, $50.3{pm}7.3%$ vs. $76.9{pm}19.6%$, p=0.014). Lower baseline $PaO_2$ on room air breathing was observed in the deteriorated group ($68.6{pm}7.8mmHg$ vs. $91.4{pm}6.6mmHg$ p=0.001). Subcutaneous IFN-${gamma}1b$ did not show better efficacy than prednisolone. Five patients discontinued IFN-${gamma}$ because of severe side effects. ARDS developed in one patient, who eventually died. Conclusion : The administration of IFN-${gamma}1b$ is not desirable for patients diagnosed with IPF with poor lung function. Long-term and large-scaled clinical studies are needed for its efficacy in IPF.