Signal detection procedures were used to examine the ability of participants to detect and label facial expressions of emotion in an upright or inverted orientation when the faces were rapid videotaped presentations. The detection and identification of facial expressions were remarkably accurate. In the upright orientation, the A' measure of sensitivity was above.9 for detection and identification of all six facial expressions of emotion. Sensitivity to inverted expressions was diminished for all emotions; however, the extent of the decline in sensitivity depended upon the specific facial expression. If the expression was difficult to detect or label in the upright orientation, the sensitivity score was lower in the inverted orientation. An assessment of the errors made in the detection and labelling process allowed a demonstration of the specific facial expressions that were confused in either the upright or inverted orientation. The assessment of sensitivity and analysis of the errors suggests that the nature of perceptual processing of some, but not all, facial expressions is changed by inversion.