Women's intra-gender hostility has been the focus of attention in both the popular media and scholarly literature. However, important gaps still remain in our understanding of the construct validity, causes of, and contextual factors influencing this process. Thus I investigate the following under-explored questions in this thesis: a) is intra-gender hostility a form of conflict unique to women, or are similar processes also evident among men?; b) do the unique identity pressures women face as a lower status group contribute to their intra-gender hostility?; and c) what contextual factors modify women's intra-gender hostility?In Chapter 3, I find that men and women report similar levels of attitudinal intra-gender hostility, indicating that it is not a form of intra-group conflict more commonly faced by women. I also demonstrate that the factor structure of men and women's intra-and inter-gender hostility are distinct, suggesting that intra-gender hostility is a form of intra-group conflict rather than an expression of general negativity. Building on this in Chapter 4, I provide more convincing evidence that women's intra-gender hostility reflects and potentially reinforces their disadvantaged position.Specifically, I demonstrate that women's intra-gender hostility is related to the unique identity pressures they face as a lower status group and factors which reflect and potentially reinforce their disadvantaged position (i.e. sexual competitiveness regarding attractiveness, hostile sexism, private collective self-esteem). In contrast, men's intra-gender hostility was uniquely related to factors which reflect and reinforce their higher status position (i.e. hostility toward men). This suggests that men and women's intra-gender hostility may function in complementary ways to reinforce the gender-related status hierarchy.In Chapter 5, I further investigate how women's unique identity pressures contribute to their intra-gender hostility. I replicate findings from previous research that women who more (versus less) strongly endorse hostile and, to a lesser extent, benevolent sexism, demonstrate greater intra-gender hostility toward non-traditional women. However, I extend these findings by demonstrating that collective threat (the concern that the poor behaviour of an ingroup will be generalised to a negative stereotype of the entire group Cohen & Garcia, 2005); partially explains hostile (but not benevolent) sexists' intra-gender hostility. This provides further evidence that the unique identity pressures women face contribute to their intra-gender hostility, and preliminary evidence to suggest that unique identity pressures related to gender-role appropriate behaviour and maintaining a positive social identity can influence women's attitudes toward and treatment of other women in certain circumstances.Finally in Chapter 6, I investigate the social psychological factors which may contextually activate or attenuate women's intra-gender hostility in the face of social identity threat. I replicate findings fro...