This document describes the segmentation guidelines for the Penn Chinese Treebank Project. The goal of the project is the creation of a 100-thousand-word corpus of Mandarin Chinese text with syntactic bracketing. The Chinese Treebank has been released via the Linguistic Data Consortium (LDC) and is available to the public. The segmentation guidelines have been revised several times during the two-year period of the project. The previous two versions were completed in December 1998 and March 1999, respectively. This document is the third and final version. We have added an introduction chapter in order to explain some rationale behind certain decisions in the guidelines. We also include the English gloss to the Chinese words in the guidelines. In this document, we first discuss the notion of word and tests for wordhood that have been proposed in the literature. Then we give the specification for word segmentation. The specification is organized according to the potential Part-of-Speech tag of an expression and the internal structure of the expression. Next, we specify the treatment for some common collocations. Finally, we compare our guidelines with two segmentation standards: the first (Liu et al., 1993) is used in Mainland China and the second (CKIP, 1996) is used in Academia Sinica in Taiwan.