We present the first results of a 2-year high-resolution spectroscopy campaign of 59 candidate gamma Doradus stars which were mainly discovered from the HIPPARCOS astrometric mission. More than 60% of the stars present line profile variations which can be interpreted as due to pulsation related to gamma Doradus stars. For all stars we also derived the projected rotation velocity (up to more than 200 km s(-1)). The amplitude ratios 2K/Deltam for the main HIPPARCOS frequency are in the range 35-96 km s(-1) mag(-1). About 50% of the candidates are possible members of binary systems, with 20 stars being confirmed gamma Doradus. At least 6 stars present composite spectra, and in all but one case (for which only one spectrum could be obtained), the narrow component shows line profile variations, pointing towards an uncomfortable situation if this narrow component originates from a shell surrounding the star. This paper is the first of a series concerning mode identification using both photometric and spectroscopic methods for the confirmed gamma Doradus stars of the present sample.