There is a major need for an empirical evaluation of classification criteria for somatoform disorders. The present study analyzes psychometric properties of the existing criteria for somatization disorder. The full sample consisted of 324 patients seeking help because of "psychosomatic problems." Data from a subsample of carefully diagnosed patients with somatization syndrome (n = 76) and a clinical comparison group (n = 32) permitted the analysis of the discriminative power of items. Twenty-one somatic symptoms adopted from DSM-IV and ICD-10 criteria did not exhibit the necessary psychometric characteristics (item probability, item-total correlation, etc.). Thirty-two somatic symptoms showed a satisfactory psychometric performance. A cut-off of seven or more symptoms yielded the best discrimination between low and high disability. New criteria for somatization syndrome ("polysymptomatic somatoform disorder") are proposed taking into account for the strong association of somatization and abnormal illness behavior.