Recent experiments exploring the use of transition radiation as an intense source of tunable, coherent x rays included a measurement of the energy spectra and angular distribution of transition radiation in the soft x-ray energy range. The radiation was produced when 25-MeV electrons penetrated a stack of eighteen 1-μm-thick beryllium foils. The most striking result is the demonstration of coherence of the photons emitted at the two surfaces of a single foil.