Spectral signature coding is an effective means of characterizing spectral features. This paper develops a rather different encoding concept, called progressive signature coding (PSC), which encodes a signature in a hierarchical manner. More specifically, it progressively encodes a spectral signature in multiple stages; each of these stages captures disjoint spectral information contained in the spectral signature. As a result of this progressive coding, a spectral profile of progressive changes in a spectral signature can be generated for spectral characterization. The proposed idea is very simple and evolved from the pulse code modulation (PCM) commonly used in communications and signal processing. It expands PCM to multistage PCM (MPCM) in the sense that a signature can be decomposed and quantized by PCM progressively in multiple stages for spectral characterization. In doing so, the MPCM generates a priority code for a spectral signature so that its spectral information captured in different stages can be prioritized in accordance with significance of changes in spectral variation. Such MPCM-based progressive spectral signature coding (MPCM-PSSC) can be useful in applications such as hyperspectral data exploitation, environmental monitoring, and chemical/biological agent detection. Experiments are provided to demonstrate the utility of the MPCM-PSSC in signature discrimination and identification.