Let D be a subset of a real partially ordered Banach space E. Let A:
be a mixed monotone operator (i.e.
is nondecreasing and
is nonincreasing). A point
is called a coupled fixed point of A if
be given by
. Note that
is increasing and the fixed point of
is the coupled fixed point of A. By using this observation and known results on fixed points, the author gives several existence theorems for coupled fixed points.