  We discuss the formation of spectral features in the decelerating ejecta of
gamma-ray bursts, including the possible effect of inhomogeneities. These
should lead to blueshifted and broadened absorption edges and resonant
features, especially from H and He. An external neutral ISM could produce
detectable H and He, as well as Fe X-ray absorption edges and lines. Hypernova
scenarios may be diagnosed by Fe K-$\alpha$ and H Ly-$\alpha$ emission lines.
