OBJECTIVE: To explore the Internet use and interpersonal interactions of youth reporting deliberate self-harm as defined by any non-fatal act, regardless of intention. METHOD: The Second Youth Internet Safety Survey is a nationally representative telephone survey of 1500 Internet users (ages 10-17) in the United States, conducted March to June 2005. RESULTS: Youth reporting deliberate self-harm in the past 6 months (3%) were significantly more likely than other youth to have a sexual screen name or to talk with people known only online about sex (35% versus 5%) and to use chat rooms (57% versus 29%). All youth were equally likely to talk online with people known in person, yet youth engaging in deliberate self-harm were significantly more likely also to have a close relationship with someone met online (38% versus 10%). Three quarters (76%) of youth reporting self-harm used instant messaging. CONCLUSION: Findings suggest that youth who engage in self-harm may be more likely to engage in online behaviors that have the potential to place them in risky situations. Programs aimed at preventing deliberate self-harm should consider adding chat room and instant messaging to their telephone hotline capabilities.