this chapter deals with the morphosyntax of Romance clitic combinations. It summarizes some data and treatments of clitic sequences, focusing on three aspects: combinatorial restrictions, orderings, and morphological irregularities.First, not all clitic combinations are allowed, as combinatorial gaps arise from both robust cross-linguistic restrictions (the Person Case Constraint, or PCC) and language-specific constraints. The former has received much attention in the recent syntactic literature. Besides the PCC, however, Romance displays various kinds of gaps, part of which are arguably due to an identity-avoidance principle whose morphological or syntactic nature is still under discussion.Second, the order of clitic elements within a cluster is rigidly set on a language-specific basis and, third, the morphological shape of the cluster does not result from the agglutination of single clitics, as morphological irregularities arise rather frequently. Previous analyses argued that these aspects are due to some sort of extrasyntactic computation, namely morphological templates, post-syntactic operations, output constraints, etc.. Such non-syntactic devices, which do not follow from any general principle of Universal Grammar, are usually postulated to account for language-specific orderings and irregularities. In fact, however, ordering phenomena and morphological irregularities seem to be systematic, with certain patterns recurring frequently across languages. The second part of the chapter aims to show that ordering phenomena and morphological irregularities are related and both may be deemed evidence of the syntactic make-up of clitic sequences. In particular, it is shown that, building on a very restrictive theory of linearization, one may deal with the variation in clitic ordering without postulating extrasyntactic levels of computation.