This presentation grows out as an attempt to investigate the way lexical and constructional representations interact within the wider context of both functional models of language (especially, Van Valin’s (2005) Role and Reference Grammar) and Cognitive Linguistics (especially, Lakoff’s cognitive model theory, Lakoff and Johnson’s 1999, and Goldberg’s constructional approach, Goldberg, 2005). In our view, the two frameworks show clear explanatory weaknesses in those areas of enquiry where the competing perspective proves to have a more solid theoretical grounding. Thus, an account of syntactic motivation carried out exclusively on the basis of the information supplied by lexical representation systems, like those postulated in some functionalist circles, has a large degree of redundancy which should be avoided for the sake of parsimony. From a different angle, constructional representation is to be combined with lexical representation and the rules that determine the way the two representational layers interact should be specified somewhere in grammar, an issue which has not been sufficiently explained in Cognitive Linguistics. In order to fill this gap, we have formulated the Lexical Construction Model. This framework consists of an inventory of lexical conceptual representations, called lexical templates, and a number of higher-level grammatical representations called constructional templates, an issue that will be explored in a separate presentation. Here we will focus our attention on the type of cognitive constraints that regulate the way lexical templates are absorbed by constructions. This unification process is governed by constructional constraints on lexical items (as would be predicted by such notions as coercion and the Override Principle, studied by Michaelis, 2003), but also by high-level metaphorical and metonymic mappings (Ruiz de Mendoza & Mairal, 2006a), which license a number of subcategorial conversion processes and account for a relevant part of their meaning effects. Among others, we explore the cognitive grounding of lexical-constructional unification processes in high-level metaphorical mappings, such as those based on the correspondences receiver-undergoer (e.g. He talked me into it; COMMUNICATIVE ACTION IS EFFECTUAL ACTION), reflexive object-undergoer (e.g. He drank himself into a stupor; A NON-EFFECTUAL ACTIVITY IS AN EFFECTUAL ACCOMPLISHMENT), and experiencer-undergoer (e.g. Peter laughed John out of the room; I was finally “listened” into existence; EXPERIENTIAL ACTION IS EFFECTUAL ACTION). Other cases of subcategorial conversion, such as those that give rise to the causative;/inchoative and the middle alternations, are more adequately accounted for in terms of the high-level metonymies PROCESS FOR ACTION and PROCESS FOR ACTION FOR (ASSESSED) RESULT respectively. Metaphor plays no role here since we are not dealing with two different kinds of transitivity relationship (e.g. one where the object is an experiencer and another where it is an undergoer), but with different (highlighted) aspects of one kind of transitivity. We find high-level metaphor and metonymy at the basis of some grammatical processes (e.g. conversion processes and constructional alternation). This extremely interesting finding is in accord with the nature of both metonymy and metaphor: metonymies are domain-internal mappings, which makes them compatible with the fact that constructional alternation highlight different aspects of one kind of transitive schema. On the other hand, we claim that metaphors are domain-external operations that motivate a corresponding grammatical process, i.e. subcategorial conversion from one transitivity type to another. Finally, we also observe that the same principles and conceptual patterns (e.g. metaphor-metonymy interaction and metonymic chaining) that constrain metaphorical and metonymic activity at other levels of analysis are operational at the grammatical level too. (Francisco Ruiz de Mendoza Ibanez and Ricardo Mairal Uson)