This thesis consists of five individual essays and an introductory chapter. The essays are all in the field of industrial dynamics and more specifically focus on firm entry and exit in Swedish industrial sectors. The essays mainly contribute to the empirical literature on entry and exit. In four of the five essays, panel data methods are used in the empirical investigation. The first essay presents the patterns of entry and exit in industrial sectors in Sweden and studies the importance of different determinants of entry and exit rates in industries. The second essay focuses on the relationship between entry and exit. The third essay has a regional perspective, focusing on regional determinants of entry and exit. It also investigates the importance of the differences in industry structure for differences in entry and exit rates across regions. The fourth chapter uses the theory of product life cycle to investigate how knowledge intensity differs in entering and exiting firms in different stages of the product life cycle. The fifth and last essay focuses on the importance of firm demography, in terms of firm size and age, for the decision to perform process R&D, product R&D or combine process with product R&D.