Face detection, the process of finding a face in a visual scene, is a critical step in face processing, yet it has received relatively little attention compared with other face processes. The present study addresses this crucial first stage by investigating the effect of inversion on face detection and by examining how individuals with developmental prosopagnosia perform on face detection tasks. Fourteen control participants and fourteen individuals with developmental prosopagnosia (DPs) were tested with two face detection tasks: (I) Face versus Non-Face, where arrays of small images were presented, one of which could contain a face and (2) Face versus Face Parts, where a two-tone face could be embedded in a larger array of similar two-tone face parts. On each trial, participants made a speeded response if a face was present in the visual display. On almost all measures both normal and prosopagnosic individuals showed strong inversion effects with significantly worse performance with inverted faces. This shows that the simple task of detection can show inversion effects comparable to those seen for other face tasks, including recognition. Finally, while there were prosopagnosics who were well within the normal range for detection, there were significant group differences, particularly for the case of the Face versus Face Parts, where prosopagnosics were worse than controls on upright but not on inverted face detection.