In this work we report preliminary results of a search for shortperiod variable stars in the open cluster NGC 6531. In particular we looked for new roAp, Delta-Scuti and gamma-Doradus stars. We collected high-precision V-Bessel time-series data with the SOAR Optical Imager (SOI) at the SOAR 4.1m telescope. The data were reduced using a custom pipeline based on IRAF/PyRAF and the final light-curves were analyzed using discrete Fourier transforms (DFT). The periods and the preliminary classifications of five newly discovered variables are discussed.