  Action of 4 dimensional N=4 supersymmetric Yang-Mills theory is written by
employing the superfields in N=4 superspace which were used to prove the
equivalence of its constraint equations and equations of motion. Integral forms
of the extended superspace are engaged to collect all of the superfields in one
"master" superfield. The proposed N=4 supersymmetric Yang-Mills action in
extended superspace is shown to acquire a simple form in terms of the master
superfield.
