This paper studies the nature of the BEI-construction in Cantonese, with Mandarin as the standard language of comparison. Although the BEI-construction has been much studied in Mandarin, the same in not true for Cantonese. Although this construction has traditionally been termed a "passive", I will show that it can have a different range of semantic interpretations in Cantonese. I argue that BEI is not confined to passive, but is used under certain circumstances to form a causative construction as well. The differences in behaviour between passive-BEI and causative-BEI can be seen in tests with anaphoric binding. I conclude that while the passive structure is mono-clausal, the causative structure must be bi-clausal. The Cantonese BEI-constructions have an obligatory agent-phrase which cannot be dropped. This differs from Mandarin and the challenge is to find an account for this phenomenon, especially if we are to claim that this construction is a passive. The optionality of the agent phrase is characteristic of passives and yet Cantonese deviates from this norm. I argue that passive in Cantonese is a syntactic process and predict that only transitive verbs may participate in this construction. I utilize the universal v-VP structure on transitive verbs, proposed by Chomsky (1995), to guarantee that the external theta role must be retained. I also examine the much debated status of BEI which is used in the BEI-construction. Although this construction can be used to derive both a passives and a causatives, it does not necessarily mean that two separate BEIs must be posited. I conclude that BEI can be treated as a category-neutral element which can interact in both causative and passive structures. To support this proposal I appeal to the functional versus lexical distinction of categories and projections.