  We review recent progress in constructing realistic brane models from type I
string vacua. Explicit models with three families of the standard model gauge
group and its left-right generalizations are presented with supersymmetry
broken at the string scale of order $M_s\sim 10^{10-12}$ GeV, realizing gravity
mediated supersymmetry breaking at low energies. Unification of couplings
occurs at the string scale due to the particular U(1) normalizations of
D-branes, as well as to the existence of a Higgs field per family of quarks and
leptons. The proton is naturally stable due to intrinsic discrete symmetries of
the corresponding string theory. In particular R-parity appears as a natural
stringy symmetry. There are axionic fields with the right couplings as to solve
the strong CP problem. Similar realizations are also presented for a string
scale of 1 TeV, although without solving the gauge unification problem. Open
questions are briefly discussed.
