Objective: Renal stone formation is one of the extra-articular manifestations of ankylosing spondylitis (AS). In these study, it is investigated whether there is a relationship between renal stone formation and intestinal inflammation in AS patients. Methods: Patients meeting the 1984 Modified New York criteria for AS were included in the study. Calprotectin levels, an indirect indicator of intestinal inflammation, were measured in each patient. Colonoscopy and, if necessary, colonoscopic biopsy were performed in patients with calprotectin level >70 υg/g. AS patients who received infliximab or adalimumab were excluded from the study. The use of non-steroidal anti-inflammatory drugs was discontinued at least 6 weeks ago. Results: Ninety AS patients (M: 57; F: 33) (renal stone +: 26; renal stone -: 64) were included in the study. The mean age of the patients was 43±10.9 years; the mean age at diagnosis was 33±10 years and the diagnosis delay was 6.2±5 years. Calprotectin level was higher in 3 patients (11.5%) with renal stones (+), while calprotectin level was higher in 9 patients (14%) with renal stones (-). Histological evidence of intestinal inflammation was found in 5 (41%) of 12 patients with high calprotectin levels. These 5 patients did not have renal stones. In 3 patients with renal stone (+) and high calprotectin levels, no microscopic signs of inflammation in the intestine were observed. Conclusion: No relationship was found between fecal calprotectin level and the presence of renal stones. Serial calprotectin measurement studies with a much higher number of patients, excluding variables that may have a role in the intestinal microenvironment, will give much more reliable results in this regard