Quantum optics in the most general sense seeks to understand the physical phenomena related to the interaction of radiation and matter. The field has therefore always been characterized by an enormous span of activities from fundamental investigations - e.g., into the nature of radiation fields - to spectroscopic methods for applied research. The 18 invited lectures presented at the seminar on "Fundamentals of Quantum Optics II" in Obergurgl, Austria, in the winter of 1987 cover the following topics: - chaos in quantum systems; - squeezed quantum states; - quantum jumps; - quantum electrodynamics in a cavity; - laser cooling and optical traps; - Rydberg atoms; - cooperative phenomena and other fundamentals. For scientists and graduate students working in quantum optics and related fields this book provides an excellent overview of new developments; it gives a clear demonstration of the surprising and characteristic speed with which this field turns fundamental insights into applications (e.g., squeezed states) and how experimental progress contributes to those fundamental insights (e.g., trapping techniques).