Technology development in firms is frequently based on a combination of internal and external technological learning. Consequently, firms need to develop both technological capital (a patent portfolio) and alliance capital (a portfolio of technology alliances). This paper examines the relationship between technological capital, alliance capital and their joint impact on the technological performance of firms, with an application to the ASIC industry. We find that positive marginal returns to alliance capital are decreasing at higher levels of alliance capital. Technological capital and alliance capital can either augment or reduce each others’ influence on innovation performance depending on the stage of the technology life cycle in the industry. A reinforcing relationship related to absorptive capacity requirements and technological uncertainty is present in early stages, while technology leakage and market competition effects render the combination of high levels of technological and alliance capital counterproductive in later stages of the technology life cycle.