Recent research on gender differences in aggressive behaviors is reviewed in this second of a two-part article on the aggression of girls. The objective here is to use findings from studies done by social scientists to confirm and extend vivid reports in recent popular texts (Hadley, 2003). Findings are first summarized and then detailed with methodological issues and some theoretical implications discussed by way of conclusion. This recent research supports observations of differences in the aggression of boys and of girls. It points to the need for further research and discussion on the topic of gender and aggression.