Mathematical ecology is a subject which recently attracts the attentions of many mathematicians and biologists. One of the most important and fundamental mathematical models in ecology is of Lotka-Volterra type. This text gives the global dynamical properties of L-V systems. The properties analyzed are global stability of the equilibria, persistence or permanence of the systems (which ensures the survival of all the biological species composed of the systems for the long term) and the existence of periodic or chaotic solutions. The special subject of this book is to consider the effects of the systems structure, diffusion of the biological species and time delay on the global dynamical properties of the systems.