Connections developed in recent years between particle physics and cosmologyare the focus of attention in this new textbook. The author describes some of the theories which have been developed to describe the fundamental interaction of elementary particles in the extremely high temperatures of the early universe, taking care to distinguish facts and well-established results from hypotheses and speculations. - The three parts of the book discuss the standard hot big bang model of the earlyuniverse, the basic ideas of the standard and the grand unified theories of elementary particles, and the influence of dark matter on the large-scale evolution of structure. In addition to making some minorcorrections the author has added an appendix presenting new results and an updated bibliography. Two main groups of readers are addressed: research students in astronomy can use this book to understand the impact of elementary particle theory on cosmology, while research students in particle physics can use it to acquaint themselves with the basic facts of cosmology. The book is written carefully enough to appeal also to a wider audience of physicists.