The authors surveyed physicians for frequency estimates of factitious disorder among their patients. Twenty-six physicians in independent practice and 83 senior hospital consultants in internal medicine, surgery, neurology, and dermatology participated. They completed a questionnaire including the estimated 1-year prevalence of factitious disorder among their patients. Frequency estimates averaged 1.3% (0.0001%-15%). The number of patients treated correlated negatively with frequency estimates. Dermatologists and neurologists gave the highest estimations. One-third of the physicians rated themselves as insufficiently informed. Frequency estimations did not differ by information level. The estimated frequency is substantial and comparable to earlier findings. Authors discuss clinical implications.