There is a general agreement that the M dwarfs constitute the most
 numerous objects in our Galaxy. Only at the faint end (Mv >= 12m)
 of the main sequence the debate is still open how the stellar
 luminosity function and mass function continue. Is there a local
 mass of the disk population or not. The DENIS Survey (Deep Near-IR
 Southern Sky Survey), a project in which some of us are directly
 participating, should discover a lot of new faint nearby dwarfs and
 contribute to a significant improvement of the stellar luminosity
 function in the solar neighborhood towards fainter magnitudes.
 However, the present estimates of the effective temperatures for
 individual objects with Teff < 4000K are quite poor (see Monet et al.
 1992,AJ 103,638), and a large fraction of the flux is emitted in the
 infra-red. It would be highly desirable to receive low-resolution
 spectra for carefully selected stars, well-distributed  along the main
 sequence, beyond the DENIS reddest band.
 As the error in absolute magnitude depends essentially on the error of
 the parallax determination, we selected stars contained in the
 Hipparcos Input Catalogue, for which very soon accurate parallaxes
 become available. So we will have the full advantage of combining ISO,
 Hipparcos and DENIS data for the proposed objects.
 The objects were selected from the Catalogue of Nearby Stars III
 (Gliese and Jahreiss, 1991, preliminary version), according to the
 following criteria: (i) single stars, or wide-pair with well-isolated
 components; (ii) not variable whenever possible; (iii) away from the
 galactic plane; (iv) no disturbing neighbours or future neighbours
 (our stars  are all high-proper motion stars, check in the HST
 Guide-Star Catalog); (v) declination south of +2 degrees, in order to
 be observed with DENIS, and used as standards; (vi) in the Hipparcos
 Input Catalogue, except one too faint for it, but with an excellent
 ground-based parallax.