The liquid state is possibly the most difficult and intriguing state of matter to model. Organic liquids are required, mainly as working fluids, in almost all industrial activities and in most appliances (e.g. in air conditioning). Transport properties (namely dynamic viscosity and thermal conductivity) are possibly the most important properties for the design of devices and appliances. Most theoretical studies on the liquid state date back to the Fifties however huge advances in experimental studies and applied research on heat and mass transfer in liquids have been achieved during past decades. Most of the models cannot rely on theory alone and are empirical, while for most organic liquids, only a few experimental points and empirical correlations are available in literature.The aim of this book is to present both theoretical approaches and the latest experimental advances on the issue, and to merge them into a wider approach. The book is organised into five chapters. The first chapter presents our theoretical knowledge of the liquid state. The second presents the tentative models for the evaluation of the thermal conductivity of organic liquids and confronts their results with the experimental data available in literature. The third presents the tentative models for the evaluation of the dynamic viscosity of organic liquids and confronts their results with the experimental data available in literature. The fourth presents a deeper review of the choice methods for thermal conductivity and their applications to mixtures of organic liquids and the fifth chapter presents a deeper review of the choice methods for dynamic viscosity and their applications to mixtures of organic liquids.