This study evaluated the Amor and European Spondylarthropathy Study Group (ESSG) classification criteria for spondyloarthropathies in Turkish patients seen from October 1990 to August 1993 at the Physical Medicine and Rehabilitation Department of the GATA Haydarpasa Training Hospital. The Amor and ESSG criteria were evaluated in 157 patients with spondylarthropathies and in 124 controls with a variety of other rheumatic diseases. The sensitivity, specificity, positive predictive value, and negative predictive value of each criteria set were calculated, as well as the sensitivity and specificity of each of the 24 criteria used in these sets. For Amor's criteria, sensitivity was 88.5%, specificity was 91.9%, positive predictive value was 93.3% and negative predictive value was 86.4%. For the ESSG criteria, sensitivity was 86.6%, specificity was 91.1%, positive predictive value was 92.5% and negative predictive value was 84.3%. No significant differences were found between the two criteria sets. Our data show that the Amor and ESSG criteria are of similar value for the classification of spondylarthropathies and are comparable in terms of sensitivity and specificity. They also demonstrate the need for monitoring patients with equivocal clinical patterns using both sets of criteria as tools that complement each other.