Fatigue is one of the major symptoms reported by sarcoidosis patients. The relationship between fatigue and clinical course of sarcoidosis remains unclear. The aim of the study was to evaluate the relationship between fatigue and lung function tests, exercise tolerance, dyspnea, and quality of life among sarcoidosis patients. One hundred eleven sarcoidosis patients completed the following questionnaires: Fatigue and Assessment Scale (FAS), Quality of Life Scale (SF-36), and dyspnea scales: Medical Research Council Questionnaire, Baseline Dyspnea Index, and Oxygen Cost Diagram. Clinical parameters (FVC, FEV1, DLCO, VO2, and VO2/AT, and work load) were derived from the patients' medical files. The exercise tolerance was the only clinical parameter associated with fatigue (Max. Work Load -0.65, VO2 -0.42, VO2/AT -0.51). No correlations were found between FAS and spirometry or diffusing tolerance. Fatigue correlated with all dyspnea domains by means of (r values ranging from 0.47 to 0.77 in multivariate regression analysis) and with quality of life in SF-36 questionnaire (r values ranging from -0.33 to -0.83). We conclude that FAS seems a reliable and valid indicator of dyspnea level, quality of life, and exercise tolerance in sarcoidosis patients.