Polarized inclusive leptoproduction, lN-->hX, and the hadron helicity density matrix rho (h): Possible measurements and predictions.

We discuss the production of hadrons in polarized lepton-nucleon interactions and in the current jet fragmentation region; using the QCD hard scattering formalism we compute the helicity density matrix of the hadron and show how its elements, when measurable, can give information on the spin structure of the nucleon and the spin dependence of the quark fragmentation process. The cases of {rho} vector mesons and {Lambda} baryons are considered in more detail and, within simplifying assumptions, some estimates are given. {copyright} {ital 1996 The American Physical Society.}