This monograph deals with the quantum kinetics for transport in low-dimensional microstructures and for ultrashort laser pulse spectroscopy. The nonequilibrium Green function theory is described and used for the derivation of the quantum kinetic equations. Numerical methods for the solution of the retarded quantum kinetic equations are discussed and results are presented for quantum high-field transport and for mesoscopic transport phenomena. Quantum beats, polarization decay and non-Markovian behaviour are treated for femtosecond spectroscopy on a microscopic basis.