Let G denote GL(2,F),
where F is R or C or a p-adic field. Let η be a non-trivial character of the unipotent
upper triangular group N in G. The object of this paper is to present an explicit
spectral decomposition of L2(N ∖G,η), the representation of G induced unitarily by
η. This representation is well-known to be multiplicity-free and to be quasi-equivalent
to the (right) regular representation of G.