  In this summary I review some results relative to: planetary nebulae, H II
regions, chemical evolution of galaxies, and the determination of the
primordial helium abundance. These results were presented during the symposium
"Ionized Gaseous Nebulae" which took place in Mexico City, Nov, 2000. To get a
more general perspective of this meeting I encourage you to read all the
contributions to the symposium proceedings.
