This study employs the island repair effect on the Left Branch Condition (LBC) to illuminate the derivation of Mandarin sluicing. It utilizes three unique properties of Mandarin island repair related to the LBC involving (i) covert antecedents, (ii) contrastive modifiers, and (iii) multiple islands including LBC structures in order to examine two deletion-based analyses of sluicing in the literature. It is shown that these analyses fail to satisfactorily explain the properties discussed. To capture the facts, a pseudosluicing analysis is proposed which claims that sluiced clauses in Mandarin are simply composed of a subject pro, an (optional) copula shi 'be', and a wh-in-situ wh-remnant serving as a predicate. The strong redemptive ability of repairing LBC effects in Mandarin is attributed to the construal of pro instead of deletion. From a typological point of view, among East Asian languages, Mandarin sluices differ from Japanese and Korean sluices in that the pro of the former cannot be interpreted as a concealed cleft structure but instead functions as an implicit subject.(iii) multiple islands involving the LBC. The paper evaluates two deletion-based analyses, the Focus condition analysis (Merchant 2001) and the multi-movement and deletion analysis (Wang 2007), and demonstrates that these analyses cannot satisfactorily explain the three concerned discrepancies and other fundamental properties in Mandarin sluicing, such as syntactic parallelism under deletion and the distribution of the copula shi 'be'. To capture these properties and patterns, a pseudosluicing analysis of sluicing in Mandarin (Wei 2004) is proposed, which explains the redemptive effect of the LBC in Mandarin via the construal of pro rather than deletion. In this sense, Mandarin sluicing is similar to pseudosluicing in English, is a base-generated structure consisting in a simple clause [pro (shi) wh-remnant], and is different from English deletion-based canonical sluicing. Additionally, it is claimed that Mandarin sluices are not concealed cleft structures resulting from argument ellipsis, unlike Japanese and Korean sluices (Nishiyama et al. 1996;Saito 2004Saito , 2007 Takahashi 2008a, b). It is proposed that the pro in Mandarin sluices can be reinterpreted as an E-type pro (Evans 1980), which explains the generation of sloppy identity readings. Quite generally, the analysis makes use of two well-established properties of Mandarin Chinese to explain its sluicing construction: the pro-drop nature of Chinese and topic-comment predication, and the fact that no new ad hoc stipulations are required in the analysis.The organization of this paper is as follows. Section 2 compares island repair effects in LBC structures in English with Mandarin Chinese. Section 3 reviews two potential deletion-centered accounts of sluicing and argues that they are not appropriate for Chinese. Section 4 then proposes the pseudosluicing analysis. Section 5 discusses the origin of the strong island/LBC repair effect in Mandarin Chinese. Section 6 further clarifies the ...