This paper is a follow-up to the earlier Primer Series paper on causal models. The earlier paper demonstrated the usefulness of causal models in designing and implementing impact assessments of private sector development (PSD) programs and in reassessing and revising program design relative to its intended impacts. The paper drew on the case study of the PROFIT Zambia project to demonstrate what a causal model is, how it works, and what its benefits are. Another benefit of the causal model alluded to in the previous Primer Series paper is its usefulness in developing a program performance monitoring system. This Primer Series paper takes up this topic and expands on it. Specifically, it demonstrates how integrating the causal model into program design and operations can guide program implementation and increase the likelihood that the program achieves its intended impacts. As in the previous paper, it draws on the PROFIT case study for demonstration.