Objective: The aim of the study is to assess the natural course of systemic sclerosis (SSc) in patients with interstitial lung involvement and to evaluate the effects of treatment. Materials and methods: Sixty SSc patients with interstitial lung involvement were included in the study and history and retrospective data records of the patients were reviewed. Results: It was observed that 47 patients (78.3%) had Raynaud's phenomenon, 7 patients (11.7%) had skin involvement, 5 patients (8.3%) had joint involvement, and 1 patient (1.7%) had gastrointestinal system involvement as the first manifestation of the disease. Lung involvement had developed on an average of 113 +/- 106 months after the first manifestation of the disease and was apparent within the first year in 10 patients (16.7%), between 1 and 2 years in 3 patients (5%), between 2 and 3 years in 2 patients (3.3%), between 3 and 4 years in 5 patients (8.3%), between 4 and 10 years in 21 patients (35%), and after 10 years in 19 patients (31.7%). When the symptoms of lung involvement appeared, 37 patients (61.7%) were not receiving treatment while 23 (38.3%) were using an immunosuppressive agent. The time interval of lung involvement for the treated patients was 131 +/- 95 months while it was 101 +/- 112 months in untreated patients (p > 0.05). Conclusion: In SSc patients with intersititial pulmonary involvement, the disease frequently starts with Raynaud's phenomenon and pulmonary symptoms tend to appear at a mean of 7 years after the onset of disease. The first sign of the disease, the probability of interstitial pulmonary involvement, is highest during the first 15 years after. Although this probability decreases after 15 years, in up to 10% of the patients, interstitial pulmonary involvement can still occur even up to 40 years. Immunosuppressive treatment is not effective in preventing the development of pulmonary involvement. However, it delays the manifestation of pulmonary symptoms for nearly 4 years.