  This investigation is aimed at clarifying the nature of the interstellar gas
seen in absorption against bright O and B stars. Towards this end we have
obtained for the first time HI absorption spectra towards radio sources very
close to the lines of sight towards 25 bright stars previously studied. In this
paper we describe the selection criteria, the details regarding our
observations, and finally present the absorption spectra. In the accompanying
paper we analyse the results and draw conclusions.
