Aims: To evaluate renal morphology, prevalence of urinary stone disease, renal perfusion and resistance to renal blood flow in patients with ankylosing spondylitis(AS). Material and methods: Thirty-eight patients diagnosed with AS and with normal basal renal functions, together with 38 healthy individuals matched in terms of age, sex, blood lipid profile and body mass index, were included. Total cholesterol, triglyceride, urea, creatinine and glucose levels were measured in both groups, as well as vitamin D, erythrocyte sedimentation rate (ESR) and C-reactive protein in the AS group. Renal dimensions, parenchymal echogenicity, presence of stone and renal resistive index (RRI) from the interlobular artery level were measured, and correlations with clinical and laboratory parameters were assessed. Results: Thirty-eight patients diagnosed with AS (age 42.4 +/- 11.5, 24 male, 14 women) and a control group of 38 healthy individuals (age 41.7 +/- 10.8, 23 male, 15 female) were included in the study. Renal stone was present in 7 patients (18.4%) in the AS group and 4 subjects (10.5%) in the control group. There was no significant difference in prevalence of stone between the groups (p=0.516). RRI values were significantly higher in the patients with AS (0.63 +/- 0.06) compared with the control group (0.59 +/- 0.03, p=0.001). Significant correlations were determined between RRI and age, triglyceride level, body mass index and length of disease. Conclusions: Renal Doppler is an important examination in early diagnosis and monitoring of renal changes in AS patients since renal complications in AS develop in the chronic and follow a subclinical course.