Energy of the vacuum with a perfectly conducting and infinite cylindrical surface

Values for the vacuum energy of scalar fields under Dirichlet and Neumann boundary conditions on an infinite clylindrical surface are found, and they happen to be of opposite signs. In contrast with classical works, a complete zeta function regularization scheme is here applied. These fields are regarded as interesting both by themselves and as the key to describing the electromagnetic (e.m.) case. With their help, the figure for the e.m. Casimir effect in the presence of this surface, found by De Raad and Milton, is now confirmed.