  This thesis carries out a detailed investigation of the action for pure Yang-
Mills theory which L. Mason formulated in twistor space. The rich structure of
twistor space results in greater gauge freedom compared to the theory in
ordinary space-time. One particular gauge choice, the CSW gauge, allows
simplifications to be made at both the classical and quantum level.
  The equations of motion have an interesting form in the CSW gauge, which
suggests a possible solution procedure. This is explored in three special
cases. Explicit solutions are found in each case and connections with earlier
work are examined. The equations are then reformulated in Minkowski space, in
order to deal with an initial-value, rather than boundary-value, problem. An
interesting form of the Yang-Mills equation is obtained, for which we propose
an iteration procedure.
  The quantum theory is also simplified by adopting the CSW gauge. The Feynman
rules are derived and are shown to reproduce the MHV diagram formalism
straightforwardly, once LSZ reduction is taken into account. The three-point
amplitude missing in the MHV formalism can be recovered in our theory. Finally,
relations to Mansfield's canonical transformation approach are elucidated.
