Some recent experimental and theoretical developments in secondary electron (SE) imaging are reviewed. Coincidence experiments identify inner-shell excitations and single electron valence excitations often as more significant initial events in SE production than the more delocalized process of plasmon generation. Quantitative measurement and interpretation of escape depths in different materials are now becoming possible. Local variations in surface barrier height or work function can be imaged, e.g. at p-n junctions in semiconductors, especially if the effects of external patch fields are overcome.