Sacroiliac index (SI index) was determined by the quantitative scintigraphy in 106 patients:28 with ankylosing spondilitis, 51 with Reiter's disease, 9 with psoriatic, 18 with unclassified seronegative spondylarthropathy and in 20 controls. For the right joint, statistically significant difference was found between the control group SI-index value and the one in patients' group (p < 0.001 to p < 0.005) except in patients with psoriatic spondylarthropathy. Analysing each group of patients separately, statistically significant difference between the SI index of both left and right joint was present only in the group with Reiter's disease (t = 2.08: p < 0.05). Increased SI-index was found in 45.28% of all patients and this also confirmed sensitivity of the applied method, while the value of test specificity was 86.96%. Correlation between sedimentation rate and SI index as well as between radiographic finding and SI index was not present. There was a positive correlation between clinical findings and Reiter's disease but only in 56% of cases. It was concluded that scintigraphy is a useful but insufficient method in the diagnosis of seronegative spondylarthropathies.