In this paper, we study some additive Schwarz methods (ASM) for the p-
version finite element method. We consider linear, scalar, self adjoin
t, second order elliptic problems and quadrilateral elements in the fi
nite element discretization. We prove a constant bound, independent of
the degree p and the number of subdomains N, for the condition number
of the ASM iteration operator. This optimal result is obtained first
in dimension two. It is then generalized to dimension n and to a varia
nt of the method on the interface. Numerical experiments confirming th
ese results are reported. As is the case for other additive Schwarz me
thods, our algorithms are highly parallel and scalable.