This paper presents a description and analysis of Clitic Climbing (CC) in contemporary European Portuguese based on a corpus of about 1,000 sentences from different genres and styles. The research goal was to explain the higher frequency of CC in informal registers, a distribution deemed strange by authors working with Spanish CC because of the common character of the phenomenon in the medieval language. Four internal factors to variation in CC are presented and linked to the mentioned external factor in terms of the semantic and pragmatic values related to CC, which hold crosslinguistically at least in the domain of Romance. The informational role of CC, a relatively unexplored subject, is described in terms of secondary topic marking whereby the clitic receives high scope interpretation with respect to the intensional operator present in the infinitival domain. Along with topicality, other factor groups point to the relevance of predicate integration, which can help or hinder the assignment of a topical interpretation to the clitic. Therefore CC turns out to be not based on stylistic preferences. Instead, it is most of all a reflection of Information Structure, which is more sharply expressed in informal registers, especially dialogues.