  The optimized $\delta$-expansion is a nonperturbative approach for field
theoretic models which combines the techniques of perturbation theory and the
variational principle. This technique is discussed in the $\lambda \phi^4$
model and then implemented in the Walecka model for the equation of state of
nuclear matter. The results obtained with the $\delta$ expansion are compared
with those obtained with the traditional mean field, relativistic Hartree and
Hartree-Fock approximations.
