  A $(0,1)$-labeling of a set is said to be friendly if the number of elements
of the set labeled 0 and the number labeled 1 differ by at most 1. Let $g$ be a
labeling of the edge set of a graph that is induced by a labeling $f$ of the
vertex set. If both $g$ and $f$ are friendly then $g$ is said to be a cordial
labeling of the graph. We extend this concept to directed graphs and
investigate the cordiality of directed graphs. We show that all directed paths
and all directed cycles are cordial. We also discuss the cordiality of oriented
trees and other digraphs.
