The objective of this study was to investigate the reliability and validity of the Turkish version of the Bath Ankylosing Spondylitis (AS) Patient Global Score (BAS-G). Seventy-one consecutive patients with AS were enrolled into the study. Patients were requested to fill in the questionnaire on the day of admission (first visit), on a second occasion within 24 h after admission (second visit) for test-retest reliability analysis, and on a third occasion for assessing sensitivity to change. Construct validity was assessed by correlation analysis with the Bath AS Functional Index (BASFI), Dougados Functional Index (DFI), Dougados Articular Index (DAI), physical examination findings, and several other parameters. Test-retest reliability analysis of individual BAS-G scores at initial and second visits showed good intraclass correlations [n=46, intraclass correlation=0.928 (0.870-0.960) and intraclass correlation=0.853 (0.725-0.920), for 1-week and 6-month scores, respectively]. Both 1-week and 6-month scores showed moderate correlations with the BASFI (r=0.586 and r=0.503, respectively, P=0.000 for both). The 1-week score also showed moderate correlation with the DFI (r=0.530, P=0.000). The 1-week score showed weak correlations with finger-to-floor distance (r=0.263, P=0.027), chest expansion (r=-0.245, P=0.039), and DAI (r=0.271, P=0.036). Change in the 1-week score at the third visit showed good correlation with the BASFI score (r=0.670, P=0.000, n=36) and moderate correlation with the DFI (r=0.440, P=0.017, n=29). The Turkish version of the BAS-G has good reliability and validity. It is a good tool for assessing patients with AS or other rheumatic diseases in clinical practice and research.