Extragalactic planetary nebulae (PNe) are very useful probes of the chemical composition and evolution due to stars in the 0.8 to 8 solar masses. These stars constitute the most numerous population in either spirals, ellipticals or irregulars. Outstanding problems in astrophysics, such as: the origin of the most common heavy elements and their distribution inside a galaxy, the chemical evolution of galaxies, the nature of the Planetary Nebula Luminosity Function (PNLF), and also the internal kinematics of the parental galaxy, can be analyzed by studying PNe. All these problems however, require deep observations of representative galaxies whose distances are accurately known. In particular, to derive the PNLF for determining the distance to a given galaxy, requires a PN sample complete in at least the two brightest magnitudes.