This concise and widely referenced monograph has been used by generations of advanced undergraduate math majors and graduate students pursuing research topics in its subject area. After discussing some mathematical preliminaries, the author presents detailed treatments of the existence and the uniqueness of a solution of the initial value problem, properties of solutions, properties of linear systems, stability of nonlinear systems, and two-dimensional systems. AUTHOR: Raimond A. Struble (1923 2013) was on the faculty of North Carolina State University from 1958 until his retirement in 1987. In addition to Nonlinear Differential Equations, he was the author of over 70 articles published in the mathematical literature. Nonlinear Differential Equations is a widely referenced text and was translated into several foreign languages.