To successfully market their products, industrial vendors must determine who participates in an organizational purchase decision and what their influence is. Previous research has shown that participation and influence can vary across products and purchase situations. Though industrial marketing researchers would agree that there are different types of purchase situations, they would disagree on a taxonomy for describing them. The author uses past research as a point of departure and proposes a structural equations model that suggests the purchase situation attributes of novelty, complexity, and importance are causal determinants of participation and influence in an industrial purchase decision. The results indicate that these constructs, especially novelty and importance, provide a plausible typology for describing participation and influence in industrial purchase situations.