Nonsuicidal self-injury (NSSI; e.g., cutting or burning the skin without suicidal intent) is a dangerous and increasingly prevalent health-risk behavior. Despite advances in NSSI research over the past decade, many aspects of NSSI remain poorly understood. In particular, there are few strong predictors of NSSI, it is unclear how positive attitudes toward NSSI develop, and there are no empirically supported treatments for NSSI. In the present study, I addressed these topics with a multi-method, experimental, and longitudinal approach. For Aim 1 of the study, I examined baseline differences between NSSI (n = 58) and control (n = 86) adult participants on NSSI-themed versions of five measures that cover different aspects of attitudes: the implicit association test (IAT); the affect misattribution procedure (AMP); explicit affective ratings; startle eyeblink reactivity; and startle postauricular reactivity. Compared to the control group, the NSSI group displayed significantly more positive attitudes on all five measures. Moreover, AMP scores and explicit ratings prospectively predicted self-cutting frequency over the ensuing six months. For Aim 2, I employed pain offset relief conditioning in an attempt to induce more positive implicit attitudes toward NSSI in the control group. This conditioning significantly diminished startle eyeblink reactivity in the context of NSSI images, but did not significantly affect any other measures. For Aim 3, I tested the ability of aversive conditioning in the NSSI group to reverse positive implicit attitudes toward NSSI and to reduce NSSI behaviors over the subsequent six months. Aversive conditioning normalized startle eyeblink and postauricular reactivity, but did not significantly affect any other measures. Results also provided preliminary support for the hypothesis that aversive conditioning prospectively reduces self-cutting. In conjunction with my other recent studies (Franklin et al., 2010; 2011, 2012, 2013), these findings have prompted a new theoretical framework called the Benefits and Barriers model of NSSI.