This paper analyzes firms' choice of a merger or a strategic alliance in bundling their products with other complementary products. Tying two products of unequal value makes them equally valuable as they become inseparable for purchase. Consequently, firms can charge a higher price for the bundled products than before. If foreclosure is not the main purpose of bundling, firms would prefer strategic alliances to mergers because mergers only intensify competition by internalizing the complementarities of two products. In equilibrium, bundling occurs only through strategic alliances. (JEL L4, L11, L13, L23)