Two experiments were conducted to test Chinese children's comprehension of count- and mass-classifiers. The participants for each experiment were 80 Chinese-speaking children between the ages of 3 and 8, plus 16 adults (recruited from Taipei, Taiwan). The results of the study indicate the following points: (1) Chinese children, in early stages of language acquisition (even as young as 3 years), honor the grammatical count-mass distinction which, as suggested by Cheng and Sybesma (1998, 1999), is reflected at the level of the classifier. (2) Chinese children are capable of making fine differentiations between and among a given set of count-classifiers. They know that the relationship between a count-classifier and an entity denoted by a noun is relatively fixed. (3) Chinese children's abilities in dealing with mass-classifiers are comparable to their abilities in dealing with count-classifiers. (4) Although there are developmental differences across the classifiers tested (presumably due to lexical learning), these differences tend to fade by age 4. (5) The general classifier ge differed in that it does not require that the entity denoted by the noun be of a particular type. This was seen even in adults to some degree. The results of this study cohere with the linguistic analysis proposed by Cheng and Sybesma that the count-mass distinction is in fact relevant in Chinese grammar. These results also cohere with the current theory in cognitive development proposed by Soja, Carey, and Spelke (1991) that the ontological constraint reflected in the count-mass distinction is available in early stages of language acquisition.