Objective. Patients with fibromyalgia have difficulty with the invisibility and medically unexplained character of the syndrome. Disbelief, lack of acceptance, and stigmatization by their spouse, family, colleagues, the health care system, and society are key issues in their lives. Nevertheless, the components of this phenomenon that we term "invalidation" are not clear. The aim of our study was to identify the definition and structure of invalidation as perceived by patients with fibromyalgia. Methods. A hierarchical cluster analysis was applied to examine everyday invalidation experiences of patients with fibromyalgia. Ninety-four statements about invalidation that were derived from interviews and a card-sorting (Q-sort) technique provided the input for this cluster analysis. Results. The hierarchical structure of invalidation showed a higher-order distinction between statements reflecting "discounting" and "understanding." Discounting was subdivided into the components "denying" and "patronizing" (consisting of "lecturing" and "overprotecting"). Understanding was subdivided into "supporting" and "acknowledging." These higher-order constructs were further subdivided into 15 lower-order clusters that reflected cognitive, affective, and behavioral aspects of invalidation. Conclusion. Invalidation as perceived by patients with fibromyalgia includes active negative social responses (denying, lecturing, and overprotecting) as well as a lack of positive social responses (supporting and acknowledging) with respect to the patient and the condition of the patient. This definition of invalidation provides a basis to quantify invalidation and to study its impact on symptom severity, quality of life, therapy adherence, therapy outcome, and other important aspects of fibromyalgia.