We apply the method of discretized light-cone quantization (DLCQ) to a theory of complex and real scalars in 3 + 1 dimensions. The theory is a generalization of the Wick-Cutkosky model, and we find agreement with work by others on this model. For comparison with DLCQ, we consider an integral-equation approach. This has led to some insight, particularly with regard to the exchange of particles with zero longitudinal momentum. When the number of particles included is the same, the integral-equation results and DLCQ results agree.