Popper's theory of science has been widely misunderstood and poorly represented in the literature on philosophy of science, over the last three decades. This book discusses the main issues in Popper's theory of science and, after giving a careful characterization of each issue, examines the main objections that have been raised against them and offers ways of circumventing them. It demonstrates that Popper's theory can guide us again to a better understanding of the aim and the structure of science.