  In this thesis, we first present a brief review of black hole radiation which
is commonly called Hawking radiation. The existence of Hawking radiation by
itself is well established by now because the same result is derived by several
different methods. On the other hand, there remain several aspects of the
effect which have yet to be clarified. We clarify some arguments in previous
works on the subject and then attempt to present the more satisfactory
derivations of Hawking radiation. To be specific, we examine the analyses in
the two recent derivations of Hawking radiation which are based on anomalies
and tunneling; both of these derivations were initiated by Wilczek and his
collaborators. We then present a simple derivation based on anomalies by
emphasizing a systematic use of covariant currents and covariant anomalies
combined with boundary conditions which have clear physical meaning. We also
extend a variant of the tunneling method proposed by Banerjee and Majhi to a
Kerr-Newman black hole by using the technique of the dimensional reduction near
the horizon. We directly derive the black body spectrum for a Kerr-Newman black
hole on the basis of the tunneling mechanism.We directly derive the black body
spectrum for a Kerr-Newman black hole on the basis of the tunneling mechanism.
