  We discuss the general transport properties of superconducting quantum point
contacts. We show how these properties can be obtained from a microscopic model
using nonequilibrium Green function techniques. For the case of a one-channel
contact we analyze the response under different biasing conditions: constant
applied voltage, current bias and microwave-induced transport. Current
fluctuations are also analyzed with particular emphasis on thermal and
shot-noise. Finally, the case of superconducting transport through a resonant
level is discussed. The calculated properties show a remarkable agreement with
the available experimental data from atomic-size contacts measurements. We
suggest the possibility of extending this comparison to several other
predictions of the theory.
