Multisomatoform disorder (MSD), defined as 3 or more medically unexplained, currently distressing physical symptoms in addition to a long (> or =2 years) history of somatization, is a prevalent and disabling disorder in which few pharmacological trials have been referred to in the literature. Thirty-five MSD patients from the Somatoform Disorders Unit of the Miguel Servet University Hospital, Zaragoza, Spain, with pain of more than 3 months as the main symptom, were treated with topiramate in doses ranging from 300-400 mg/day. Patients were assessed at baseline and at one and six-months follow-up with the McGill Pain Questionnaire (MPQ), Pain Visual Analogue Scale (PVAS), Clinical Global Impresión (CGI), Global Assessment Functioning (GAF) and Hospital Anxiety Depression Scale (HADS). Eight patients (22.8%) dropped from the study, 3 due to side-effects and the other 5 because of lack of efficacy. All the outcome measures showed significant improvements at one-month except the ratings on the Hospital Anxiety Depression Scale. At six-months follow-up, clinician-rated assessments (CGI and GAF) still showed significant differences with baseline but less significant than at one-month follow-up. However, patient-rated assessments (MPQ and PVAS) did not present significant differences with baseline. Despite limitations of the study, topiramate seems to be effective in treating multisomatoform disorder patients with pain as the main symptom and a controlled randomized trial in these patients appears warranted. A possible "decay effect" in patient-rated assessments with any drug in somatoform disorder patients is discussed.