This monograph provides an overview of recent developments in and new applications for multinomial processing tree (MPT) modeling in cognitive psychology and related fields.Multinomial models are a class of stochastic models tailored to specific research paradigms that allow the measurement of latent cognitive processes underlying observed responses. An introductory review and literature survey in this monograph outlines the family of MPT models, the typical steps in MPT model analyses, the use of MPT models in cognitive psychology, statistical considerations, and computer programs for MPT modeling.Original research articles then present novel MPT modeling approaches in different fields, including episodic memory, binary choice models and "guessing", and word identification in early reading. Discussions of matters such as cognitive psychometrics and ongoing developments of MPT modeling throughout the contributions clearly demonstrate how active this field of research is and the wide range of applications of multinomial modeling.