Prosopagnosia, or face blindness, is a term designating the inability to recognize people by their face only. Until 2001, the few cases reported in the literature were almost all of the acquired form and the inborn form, with less than 20 case reports, was thought to be even rarer. In 2006, we showed that hereditary (syn. congenital) prosopagnosia belongs to one of the most common cognitive dysfunctions with a prevalence rate of 2.49 % in the German Caucasian population. Following previous work, we extended the study to 17 populations from 13 countries on four continents. The observed overall prevalence rate of 0.93% (range 0.26% - 2.47%) of the populations studied worldwide is in the same order of magnitude. This is a minimal estimate, as only 41% of the subjects who were highly suspected of prosopagnosia allowed for a follow-up examination. Extrapolating this frequency to a complete coverage, the expected prevalence rate is 2.29%. Whenever we had access to family history, we found at least one first degree relative with prosopagnosia showing that this cognitive dysfunction is highly hereditary.