Machine Translation (MT) need not be confined to inter-language activities. In this paper, we discuss inter-dialect MT in general and Cantonese-Mandarin MT in particular. Mandarin and Cantonese are two most important dialects of Chinese. The former is the national lingua franca and the latter is the most influential dialect in South China, Hong Kong and overseas. The difference in between is such that mutual intelligibility is impossible. This paper presents, from a computational point of view, a comparative study of Mandarin and Cantonese at the three aspects of sound systems, grammar rules and vocabulary contents, followed by a discussion of the design and implementation of a dialect MT system between them.