In this paper the process of exit and entry of firms in the Swedish manufacturing industry is investigated within the framework of the product life cycle. The product life cycle theory explains how the high degree of uncertainty, as regards product designs and production methods, which is connected to the early stages of the product life cycle requires a high level of knowledge-intensity. Since uncertainty decrease over the product life cycle, less knowledge is needed in production during later stages of the product life cycle. This implies that knowledge-intensity differs for firms that exit and enter in different stages of the product life cycle. Four hypotheses regarding these relationships are stated and empirically tested in this paper, using data at the 5-digit SIC-level for the Swedish manufacturing industry during 1990-1996. The empirical results show that entrants in the early stages of the product life cycle are more knowledge-intensive than incumbent firms. It is also found that firms exiting in early stages of the product life cycle are more knowledge-intensive than firms exiting in later stages.