  Peculiarities of transport properties of three- and two-dimensional
half-metallic ferromagnets are investigated, which are connected with the
absence of spin-flip scattering processes. The temperature and magnetic field
dependences of resistivity in various regimes are calculated. The resistivity
is proportional to T^{9/2} for T<T* and to T^{7/2} for T>T*, T* being the
crossover temperature for longitudinal scattering processes. The latter scale
plays also an important role in magnetoresistance. The contribution of
non-quasiparticle (incoherent) states to the transport properties is discussed.
It is shown that they can dominate in the temperature dependence of the
impurity-induced resistivity and in the tunnel junction conductivity.
