  A graph is said to be {\em half-arc-transitive} if its automorphism group
acts transitively on the set of its vertices and edges but not on the set of
its arcs. With each half-arc-transitive graph of valency 4 a collection of the
so called {\em alternating cycles} is associated, all of which have the same
even length. Half of this length is called the {\em radius} of the graph in
question. Moreover, any two adjacent alternating cycles have the same number of
common vertices. If this number, the so called {\em attachment number},
coincides with the radius, we say that the graph is {\em tightly attached}. In
{\em J. Combin. Theory Ser. B} {73} (1998) 41--76, Maru\v{s}i\v{c} gave a
classification of tightly attached \hatr graphs of valency 4 with odd radius.
In this paper the even radius tightly attached graphs of valency 4 are
classified, thus completing the classification of all tightly attached
half-arc-transitive graphs of valency 4.
