  We present semi-empirical model chromospheres computed with the atmosphere
code PHOENIX. The models are designed to fit the observed spectra of five mid-
to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used
various metal lines, e. g. from Fe {\sc i}, for the comparison between data and
models. Our computations show that an NLTE treatment of C, N, O impacts on the
hydrogen line formation, while NLTE treatment of less abundant metals such as
nickel influences the lines of the considered species itself. For our coolest
models we investigated also the influence of dust on the chromospheres and
found that dust increases the emission line flux.
  Moreover we present an (electronically published) emission line list for the
spectral range of 3100 to 3900 and 4700 to 6800 \AA for a set of 21 M dwarfs
and brown dwarfs. The line list includes the detection of the Na {\sc i} D
lines in emission for a L3 dwarf.
