OBJECTIVE Interstitial lung disease (ILD) frequently complicates systemic sclerosis (SSc). Cyclophosphamide (CYC) is a promising immunosuppressive therapy for SSc-related ILD. Our objective was to investigate the effectiveness of an intravenous CYC (iv CYC) pulse regime in SSc-related ILD during treatment and thereafter. METHODS In a prospective observational study ten consecutive patients with SSc-related ILD were treated with iv CYC in a pulse regime lasting from 6 to 24 months. Clinical status, pulmonary functional testing (PFT) and high resolution computed tomography (HRCT) of the chest were evaluated at enrolment and 6, 12 and 24 months thereafter. After treatment withdrawal, patients were followed up every 6 months with PFT and chest HRCT to monitor lung disease. RESULTS Clinical improvement was apparent in 8 out of 10 patients. The median values of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and diffusion lung capacity for carbon monoxide (DLCO) as well as ground-glass pattern on HRCT did not change significantly after 6, 12 and 24 months of therapy. The follow-up continued in 8 out of 10 patients after treatment withdrawal for a median of 26.5 months (range: 12-48 months). The final median FVC was 54.5% of predicted value (interquartile range, IQR= 31.6%-94%). Only one patient suffered a FVC deterioration greater than 10%, even though less than 160 ml. The final median DLCO was 68% of predicted value (IQR=38.3-83.6%). Only 2 patients who developed pulmonary arterial hypertension deteriorated their DLCO values of more than 15%. CONCLUSIONS An iv CYC pulse regimen over 24 months may stabilize pulmonary activity in patients with SSc-related ILD during the course of treatment and for a median of 26.5 months thereafter.