The authors studied the prevalence and characteristics of different forms of victimization in 95 patients suffering from chronic fatigue syndrome (CFS) or fibromyalgia (FM) compared with a chronic disease group, including rheumatoid arthritis (RA) and multiple sclerosis (MS) patients, and a matched healthy control group. The authors assessed prevalence rates, nature of victimization (emotional, physical, sexual), life period of occurrence, emotional impact, and relationship with the perpetrator by a self-report questionnaire on burdening experiences. CFS and FM patients showed significantly higher prevalences of emotional neglect and abuse and of physical abuse, with a considerable subgroup experiencing lifelong victimization. The family of origin and the partner were the most frequent perpetrators. With the exception of sexual abuse, victimization was more severely experienced by the CFS/FM group. No differences were found between healthy control subjects or RA/MS patients, and between CFS and FM patients. These findings support etiological hypotheses suggesting a pivotal role for chronic stress in CFS and FM and may have important therapeutic implications.