  In inclusive deep-inelastic lepton-hadron scattering multi-photon exchange
between the leptonic and the hadronic part of the process causes single spin
asymmetries. The asymmetries exist for a polarized target as well as a
polarized incoming or outgoing lepton, if the polarization vector has a
component transverse with respect to the reaction plane. The spin dependent
parts of the single polarized cross sections are suppressed like $\alpha_{em}
m_{pol}/Q$ - where $m_{pol}$ denotes the mass of the polarized particle -
compared to the leading terms of the cross section for unpolarized or
double-polarized deep-inelastic scattering. Both the target and the beam spin
asymmetry are evaluated in the parton model. In the calculation only
quark-quark correlators are included. While this approximation turns out to be
justified for the lepton spin asymmetries, it is not sufficient for the target
asymmetry.
