The conceptualization of somatization and what were previously termed somatoform disorders has changed substantially in the DSM-5 compared with previous diagnostic systems. The current diagnostic criteria for somatic symptom disorder (SSD) require the presence of symptoms (Criterion A) combined with a substantial impact of these symptoms on thoughts, emotions, and behaviors (Criterion B). In this issue of Psychosomatic Medicine, Toussaint et al. describe the development and empirical validation of a self-report questionnaire --the SSD-12--to assess the new psychological criteria (the "B criteria") of DSM-5 SSD. This is an important contribution because previously there was no questionnaire available to assess the B Criterion of SSD. The new DSM-5 criteria for SSD no longer require the absence of an adequate medical explanation for a somatic symptom, but rather define positive diagnostic criteria, focusing on the psychological impact of the somatic symptoms rather than their purported (medical) cause. Although this new conceptualization of somatization-related disorders has several advantages, seriously ill medical patients may well score high on the B Criterion for SSD on that basis alone and not because their psychological response to the medical illness is disproportionate or excessive. Measures of medical morbidity therefore need to be included in the interpretation of the SSD in individuals with severe medical conditions. Given the revised DSM-5 criteria, the newly developed and validated SSD-12 is a useful tool for diagnosing and monitoring treatment response in SSD.