The detection of discrete X-ray spectral features during the afterglows of gamma-ray burst is an important and difficult measurement, which will undoubtedly provide indispensable clues to help us understand the physical nature of the burst progenitor star. Several interesting cases have been reported, but the reality of the detections as well as their identifications and interpretations remain rather controversial. I will give a brief review the current status of X-ray emission line detections in GRB afterglows, some of the existing models, and the prospects for detecting them with present and future observatories.v