  We investigate the effects of strong magnetic fields on the equation of state
of dense stellar neutrino-free and neutrino-trapped matter. Relativistic
nuclear models both with constant couplings (NLW) and with density dependent
parameters (DDRH) and including hyperons are considered . It is shown that at
low densities neutrinos are suppressed in the presence of the magnetic field.
The magnetic field reduces the strangeness fraction of neutrino-free matter and
increases the strangeness fraction of neutrino-trapped matter. The mass-radius
relation of stars described by these equations of state are determined. The
magnetic field makes the overall equation of state stiffer and the stronger the
field the larger the mass of maximum mass star and the smaller the baryon
density at the center of the star. As a consequence in the presence of strong
magnetic fields the possibility that a protoneutron star evolves to a blackhole
is smaller.
