This paper describes the notation and underlying organization of an augmented, recursive-transition network grammar and illustrates how such a grammar is a natural medium for expressing and explaining a wide variety of facts about the psychological processes of sentence comprehension. A general discussion of transformational grammar and psycholinguistics serves as background information. Details on the structure, characteristics, and operation of the augmented, recursive-transition network grammar are provided. There is a discussion concerning the formalization of perceptual strategies and how these strategies can be naturally represented in transition network grammars. A concluding section explains the justification of transition network models. A list of references is included, and diagrams illustrate the working of the grammar in several problem areas. (VM)