A fast fashion system combines quick response production capabilities with enhanced product design capabilities, to both design “hot”products that capture the latest consumer trends and exploit minimal production leadtimes to match supply with uncertain demand. We develop a model of such a system, and compare its performance to three alternative systems: quick response-only systems, enhanced design-only systems, and traditional systems (which lack both enhanced design and quick response capabilities). In particular, we focus on the impact of each of the four systems on “strategic”or forward-looking customer purchasing behavior, i.e., the intentional delay in purchasing an item at the full price to obtain it during an end-ofseason clearance. We find that enhanced design helps to mitigate strategic behavior by offering consumers a product they value more, making them less willing to risk waiting for a clearance sale and possibly experiencing a stock-out. Quick response mitigates strategic behavior through a different mechanism: by better matching supply to demand, it reduces the chance of a clearance sale. Most importantly, we find that while it is possible for quick response and enhanced design to be either complements or substitutes, the complementarity effect tends to dominate. Hence, when both quick response and enhanced design are combined in a fast fashion system, the firm typically enjoys a greater incremental increase in profit than the sum of the increases resulting from employing either system in isolation, roughly by a factor of two in our numerical experiments. Furthermore, complementarity is strongest when customers are very strategic. We conclude that fast fashion systems can be of significant value, particularly when consumers exhibit strategic behavior.