This paper explores conventional metonymies in contemporary Mandarin Chinese in Taiwan from the perspectives of Cognitive Grammar and Conceptual Metaphor Theory. Two basic cognitive models are proposed: (1) conceptual domains and (2) scripts or scenarios. Each of these two models can serve as an interface between metonymic thought and language. They also integrate linguistic knowledge with knowledge of the world, providing a mental access to the metonymic target. A metonymic linkage exists between (1) two concepts within the same cognitive model or (2) a whole cognitive model and a certain concept within that model. According to the metonymically linked concepts or models, metonymies are grouped into three categories: part for whole, whole for part, and part for part. Adopting such a consistent approach we can stop the proliferation of metonymical categories and account for all instances of conventional metonymies in contemporary Mandarin Chinese in Taiwan.