  The leading and sub-leading order results for pion electroproduction in
polarized and unpolarized semi-inclusive deep-inelastic scattering, are
considered putting emphasis on transverse momentum dependent effects appearing
in azimuthal asymmetries. In particular the spin-dependent (single, double) and
spin-independent asymmetries of the distributions in the azimuthal angle of the
pion related to the lepton scattering plane are discussed.
