This book provides a summary of the research conducted at UCLA, Stanford University, and UCSD over the last five years in the area of nonlinear dyn- ics and chaos as applied to digital communications. At first blush, the term “chaotic communications” seems like an oxymoron; how could something as precise and deterministic as digital communications be chaotic? But as this book will demonstrate, the application of chaos and nonlinear dynamics communications provides many promising new directions in areas of coding, nonlinear optical communications, and ultra-wideband commu- cations. The eleven chapters of the book summarize many of the promising new approaches that have been developed, and point the way to new research directions in this field. Digital communications techniques have been continuously developed and refined for the past—fifty years to the point where today they form the heart of a multi-hundred billion dollar per year industry employing hundreds of thousands of people on a worldwide basis. There is a continuing need for transmission and reception of digital signals at higher and higher data rates. There are a variety of physical limits that place an upper limit on these data rates, and so the question naturally arises: are there alternative communication techniques that can overcome some of these limitations? Most digital communications today is carried out using electronic devices that are essentially “linear,” and linear system theory has been used to c- tinually refine their performance. In many cases, inherently nonlinear devices are linearized in order to achieve a certain level of linear system performance.