Although a wide body of research on sex-gender differences with White middle-class children in the United States has supported the separate worlds hypothesis (SWH), research with children from other cultures, including Taiwan, and Latino and African American children in the United States have challenged the view of girls' language as cooperative. In this study, we examine the linguistic strategies by which middle-class girls and boys from the United States and Mainland China manage conflict. Preschoolers were videotaped playing with peers. In same-sex groupings, Chinese girls and U.S. boys used the most direct strategies, including third-party complaints and censures and aggravated commands. Chinese boys used a combination of direct and indirect conflict strategies. U.S. girls used the most mitigated strategies. The pattern found in the United States of boys being more assertive than girls supported the SWH, whereas the pattern found in China was the reverse. Possible explanations of this cultural difference are provided. In cross-sex conflict in both cultures, girls dominated in some contexts but not others, suggesting contextual complexity in the consequences of conflict strategies. Results challenge the portrait of girls' language that the SWH and other gender-language models have posited.