  In this article we study the nonvanishing of cuspidal cohomology for GL(n).
Using endoscopic transfer from various classical groups we construct cuspidal
representations of GL(n) of cohomological type while working over a totally
real field or a totally imaginary quadratic extension of a totally real field.
Generalizing a construction of Laurent Clozel, we also prove nonvanishing of
cuspidal cohomology of GL(2n) over any number field but only for coefficient
systems coming from parallel weights. Working at an arithmetic level, we also
draw some inferences on an endoscopic stratification of inner cohomology of
GL(n).
