In very severe interstitial lung disease associated with connective tissue disease (CTD-ILD), progressing despite maximal conventional immunosuppression, there is no effective medical rescue therapy. The aim of the present study was to test whether rituximab, a monoclonal antibody that depletes peripheral B lymphocytes, is effective as rescue therapy in very severe CTD-ILD, unresponsive to conventional immunosuppression. We performed a retrospective assessment of eight patients with severe and progressive CTD-ILD treated with rituximab. In six patients, change in pulmonary function tests (PFTs) compared with pre-rituximab levels, was assessed at 9-12 months post-treatment. In two patients, who were mechanically ventilated at the time of treatment, clinical and HRCT changes were assessed. Seven out of eight patients had a favourable treatment response to rituximab, while in one patient disease severity did not change. In contrast with previous progression, we observed a median significant improvement of 22% in diffusing capacity for carbon monoxide (from a median baseline of 25%; range 16-32%; p=0.04), and a median significant improvement of 18% in forced vital capacity (from a median baseline of 45%; range 37-59%; p=0.03), in the 9-12 months following treatment with rituximab. In very severe CTD-ILD unresponsive to conventional immunosuppression, rituximab may represent an effective, potentially life-saving, therapeutic intervention.