On type II superstrings in less than four dimensions

We study gauge theories which are associated with classical vacua of pertur bative type II string theory that allows for a conformal field theory descr iption. We show that even if we compactify seven spatial dimensions (allowi ng for one macroscopic dimension to arise non-perturbatively) the Standard Model cannot be obtained from the perturbative sector of type H superstring s. Therefore, the construction of the Standard Model (or extensions thereof ) from M theory must involve fields that are non-perturbative from the type II perspective. We also address the case of eight compact dimensions. (C) 2001 Elsevier Science B.V. All rights reserved.