This study examined the relationship among mental health symptoms, drug treatment use, and needle sharing in a sample of 507 injection drug users (IDUs). Mental health symptoms were measured through the ASI psychiatric scale. A logistic regression model identified that some of the ASI items were associated with needle sharing in an opposing direction. Specifically, anxiety was significantly and positively associated with needle sharing. Using psychotropic medication was significantly and negatively associated with sharing needles. Those who had higher levels of drug injecting were more likely to share needles and those with an HIV-positive status were less likely to share needles. Finally, IDUs who reported high levels of drug treatment use (in the 75th percentile in terms of number of treatment admissions) were also more likely to share needles. Results suggest that treating mental health problems in IDUs who are not drug free could reduce HIV risk behaviors. The results also suggest the need to develop new intervention methods for high-level drug treatment users who may be "cycling" through treatment with low levels of treatment completion.