This self-contained book is an up-to-date description of the basic theory of molecular gas dynamics and its various applications. The progress in the field over the last thirty years has greatly enhanced the original theory and has stimulated interesting and critical gas dynamic phenomena and problems. 'Molecular Gas Dynamics,' unique in the literature, presents working knowledge, theory, techniques, and typical phenomena in rarefied gases for theoretical development and application.Basic theory is developed in a systematic way and presented in a form easily applied for practical use. After presenting various simple flows, such as unidirectional or quasi-unidirectional flows, and flows around a sphere, the author discusses additional topics, including: flows induced by temperature fields, which are typical in rarefied gases flows with evaporation and condensation bifurcation of flows in rarefied gases the ghost effect in gases in the continuum limitAn appendix contains many useful fundamental formulas, as well as an explanation of the theoretical background of the direct simulation Monte Carlo method (DSMC method), easily accessible to non-mathematicians, which is not found elsewhere in the literature.Discovery of the ghost effect has made molecular gas dynamics indispensable to the study of a gas in the continuum limit, which is traditionally treated by classical fluid dynamics. In this work, the ghost effect and non-Navier-Stokes effects are demonstrated for typical examples-Benard and Taylor-Couette problems-in the context of a new framework. A new type of ghost effect is also discussed, and a long-standing problem-bifurcation of the plane Couette flowin classical fluid dynamics-is resolved.The book is useful for those working in different communities where kinetic theory or fluid dynamics is important: graduate students, researchers, and practitioners in theoretical physics, applied mathematics, and various branches of engineering. The work may be used as a self-study reference or as a textbook in graduate-level courses in fluid dynamics, gas dynamics, molecular gas dynamics, kinetic theory, and applied mathematics.