Introduction: The aim of this study was to evaluate the cellular composition of induced sputum (IS) in sarcoidosis and its role in assessing the disease activity. The safety of the procedure was also determined. Material and methods: Sputum induction by inhalation of hypertonic saline was performed. Twenty-one samples from the healthy controls, 32 from patients with active disease, and 33 from subjects with inactive disease were analysed. Results: The percentage of lymphocytes in IS was significantly higher in active sarcoidosis than in inactive disease and the control group (9.7% vs. 3.1% vs. 2.9%), and was the highest in the patients with parenchymal changes and active disease (13.3%). The percentage of macrophages was significantly lower in active sarcoidosis than in normal subjects (76.8% vs. 83.4%). It was also significantly lower in IS in active disease and stages II and III than in both subgroups with active and inactive stage I of sarcoidosis. There were no significant differences in the IS cell percentages between the whole sarcoidosis group and the controls. Sputum induction was well tolerated and stopped only four times, two of them because of dyspnoea or the decrease of PEF. The symptoms were well reversible after administering salbutamol. Conclusions: Sputum induction by inhalation of hypertonic saline is safe, but the evaluation of IS differential cell counts is not useful in sarcoidosis diagnosing. However, it could be used in assessing the activity of the disease, especially in patients with interstitial lung changes.