Local HII galaxies present a Fundamental Plane of [L–σ] where either the equivalent width of Hβ or the oxygen abundance O/H act as a second parameter. These relations are powerful cosmological distance indicators since emission line galaxies may be found to high redshifts, though some caution must be taken till systematic effects are better understood.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html