Language comprehension requires the rapid integration of different types of information in order to arrive at an interpretation. Because the interpretation of a sentence is strongly constrained by its syntactic structure, readers and listeners must make at least partial syntactic commitments as a sentence unfolds, even when its syntactic structure is temporarily ambiguous. At the same time, a variety of constraints from the local sentence and discourse context will be available that could inform these commitments. Determining what these constraints are, and how and when they are used, is a prerequisite for understanding syntactic processing, and it is crucial for understanding the overall organization of the language processing system as a whole. Thus it is of central importance to the larger endeavor of understanding language comprehension in both normal and impaired populations. The current proposal is aimed at elucidating the mechanisms underlying syntactic ambiguity resolution within a constraint-based framework that emphasizes rich lexical representations, parallels between syntactic ambiguity and the incremental updating of a discourse model. We will explore the effects of--and the interactions among--several important sources of information, including the frequency of lexical forms and their argument structures, the thematic fit between a phrase and a potential argument position, and the effects of syntactically-relevant information from the discourse context. These goals are achieved through a combination of psycholinguistic experimentation using a variety of tasks designed to tap immediate processing (including monitoring eye-movements), analyses of corpora, and statistical and neural network modeling. We also develop a relatively novel line of research in which eye-movements to visual objects are monitored as people follow spoken instructions to manipulate the objects. The eye-movements can shed light on how people integrate visual and linguistic information and how visual context is used to resolve temporary ambiguities in spoken language.