A study examined young children's use of the Mandarin "jiu" in its adverbial form in conditional sentences. The language corpus included: (1) spontaneous speech samples of 66 children aged 4, 5, 6, and 7 years in 20 Taiwan locations and (2) story repetitions by 461 4-, 5-, and 6-year-olds in 22 locations. The data indicate that children as young as 4 years old probably comprehend several different meanings of "jiu," but primarily use the emphatic meaning in their spontaneous speech. In the repetition study, sentences with time adverbs are simpler and shorter than those with conditionals. If the children did not grasp the conditional sense of the sentences beyond the time sequence, there is no reason for them to be more likely to repeat "jiu" in the conditional sentences. Thus, the differences in repetition of jiu are an indication that the children can differentiate the conditional and temporal uses of the word. The results also suggest that more restricted experimental studies such as the repetition study can complement collection of spontaneous speech data to give a better understanding of children's language development. (MSE)