Family-of-origin aggression (FOOA) is an established risk factor for adult partner aggression. The research presented in this thesis tested a model proposing that (FOOA) is mediated through attachment and attributions to influence male and female partner aggression and withdrawal in early stage couple relationships. Study 1 tested the influence of FOOA, attachment, and attributions on partner aggression in a sample of 73 newlywed couples. FOOA was associated with male-to-female aggression, but not female-to-male aggression. Therefore the hypothesis that the influence of FOOA on partner aggression was mediated through attachment and attributions was tested only for men. Attachment was significantly associated with attributions, but there was no association between FOOA and attachment or between attributions and male partner aggression. Study 2 tested the influence of FOOA, attachment, and attributions on partner aggression and withdrawal in a sample of 101 dating couples. Structural equation model analyses found different results for men and women. For male partner aggression, the influence of FOOA was partially mediated through attachment and attributions. For male withdrawal, the influence of FOOA on withdrawal was fully mediated through attachment and attributions. The association between FOOA and withdrawal was also mediated through attachment independent of attributions, and through attributions independent of attachment. For female partner aggression and female withdrawal, the predicted associations were found for the attachment anxiety models but not for the attachment avoidance models. The current findings suggest that attachment and attributions should be intervention targets for improving relationship outcomes. The gender differences in model fit emphasise the importance of investigating risk factors for partner aggression and withdrawal separately for men and women.