  We propose a solution to the problem of renormalizing light-cone Hamiltonian
theories while maintaining Lorentz invariance and other symmetries. The method
uses generalized Pauli--Villars regulators to render the theory finite. We
discuss the method in the context of Yukawa theory at one loop and for a
soluble model in 3+1 dimensions. The model is studied nonperturbatively.
Numerical results obtained with use of discretized light-cone quantization,
special integration weighting factors, and the complex symmetric Lanczos
diagonalization algorithm compare well with the analytic answers.
