Although face perception impairments have been critical to theories of face processing, understanding of these impairments remains very limited. I will address fundamental issues in face perception via three types of face perception impairments: developmental prosopagnosia, acquired prosopagnosia, and transcranial magnetic stimulation (TMS) in normals. Results from developmental prosopagnosics required to match faces presented briefly in either the left or right visual field show that most developmental prosopagnosics have deficits in the right hemisphere but not the left hemisphere. Next predictions of two alternative models of face perception are tested with KE, a 49-year-old man with lesions affecting the fusiform face area (FFA). KE’s normal expression processing coupled with impaired identity processing support models in which expression and identity involve separate perceptual mechanisms. The necessity of regions other than the face-selective areas is demonstrated by results from KH, a 25-year-old woman who underwent a selective amygdalo-hippocampectomy. She exhibits bilateral FFA, bilateral occipital face area (OFA), and bilateral activations in the superior temporal sulcus yet experiences impairments for all aspects of face processing tested. Finally, TMS is used to reveal that the right OFA contributes to face part discrimination early in the face processing stream.