Cosmic ray physics has recently attracted a great deal of attention from the high energy physics community because of the discovery of new sources and the advent of new techniques. The result of a series of lectures prepared for graduate students and postdoctoral researchers, this book is a general introduction to experimental techniques and results in the field of ultrahigh energy cosmic rays. It succinctly summarizes the rapidly developing field, and provides modern results that include data from newer detectors. Combining experiment and theory, the text explores the results of a single, easy-to-understand experiment to tie together various issues involved in the physics of ultrahigh energy cosmic rays.