  The atmospheres of M stars are dominated by a small number of very strong
molecular compounds (H$_2$O, TiO, H$_2$, CO, VO). Most of the hydrogen is
locked in molecular H$_2$, most of the carbon in CO; and H$_2$O, TiO and VO
opacities define a pseudo-continuum covering the entire flux distribution of
these stars. The optical ``continuum'' is due to TiO vibrational bands which
are often used as temperature indicators for these stars. These may be the
depth of the bands relative to the troughs in between them; or the depth of the
VO bands; or of the atomic lines relative to the local ``continuum''; or even
the strength of the infrared water bands; all of these depend on the strength
of the TiO bands and the amount of flux-redistribution to longer wavelengths
exerted by them. Departures from LTE of the Ti I atom, and thus the
concentration of the important TiO molecule, could, therefore, have severe and
measurable consequences on the atmospheric structure and spectra of these
stars.
  In this paper we discuss NLTE effects of Ti I in fully self-consistent models
for a few representative M/Brown dwarf and M giant model atmospheres and
spectra.
