OBJECTIVE: To investigate the role of azathioprine in maintaining improvement after 1-year low-dose IV pulse CYC therapy in patients with early diffuse Systemic Sclerosis (dcSSc). METHODS: Thirteen patients with early dcSSc who had completed a year of treatment with low-dose IV pulse CYC underwent AZA treatment (100 mg/day) in a prospective 1-year study. Modified Rodnan skin score (mRss), Health Assessment Questionnaire-Disability Index (HAQ-DI), forced vital capacity (FVC), and diffusing lung capacity for CO (DLCO) were assessed as outcome measures. In addition, the nine organ/system Medsger et al. severity scores and the European Scleroderma Study Group (ESSG) activity index were evaluated. RESULTS: The improvement from a year of CYC therapy was maintained by AZA treatment. No outcome measures deteriorated (mRss 8.23 +/- 2.9 vs. 6.38 +/- 3.4; HAQ-DI 0.38 +/- 0.4 vs. 0.32 +/- 0.3; FVC 89.5 +/- 13.2 vs. 89.4 +/- 15.9; DLCO 73.6 +/- 14.4 vs. 75.0 +/- 19.5), nor were there any increases in any organ/system severity scores or ESSG activity index detected. CONCLUSION: This study suggests a role of AZA in maintaining the improvement induced by low dose pulse CYC in early dcSSc, making it possible a short duration of treatment at a low cumulative dose of the drug. These results, however, await confirmation in controlled studies.