In this important work of linguistic analysis, Paul M. Postal addresses a paradigm anomaly in French that has hitherto resisted explanation. A general restriction limiting the form of direct objects in complex infinitival constructions with main verbs like faire fails to hold with certain subordinate verbs, especially connaitre. Marshaling extensive evidence, Postal argues that this apparent irregularity is a symptom of a deeper regularity. Rather than being an ordinary transitive complement, the subordinate clause in these cases is actually an Inversion structure, one in which the logical subject demotes to indirect object. However, since this demotion induces no word order change or other direct morphological consequences, the inversion is "masked," and revealed only by several types of apparent anomalies. This analysis has significant consequences for contemporary syntactic theories. First, the arguments support the view that a sentence's superficial structure cannot be identified with its syntactic structure, even though such an identification is a fundamental assumption of several currently influential grammatical frameworks. Second, even certain theories that do posit abstract aspects of grammatical form fail to allow for the needed Inversion structures. Postal's study supports theories based on the notion of arc and stratification into levels which provide a natural treatment consistent with the factual requirements. Masked Inversion in French is the first systematic account of this puzzling French syntactic anomaly, and its findings will stimulate research in many areas of natural language grammatical structure.