These data are internally consistent and lead to several conclusions, as follows: Elevated levels of psychiatric symptoms were found among IDUs in methadone treatment as compared to their counterparts who were out of treatment. IVDUs who entered treatment had higher symptom levels than those who did not enter treatment. Higher symptom levels were found among injectors than noninjectors, and needle sharers had especially high psychiatric symptom levels. Higher symptom levels were found among those who seroconverted in the 6 months following notification, but not thereafter. Symptom levels did not distinguish between HIV-positive and HIV-negative individuals 24 months following notification of seropositivity. Taken together, these findings indicate that elevated psychiatric symptoms are risk factors for continued high risk behavior, as well as for seroconversion. The data add to those of Brooner and colleagues (1993), who demonstrated that ASPD serves as a risk factor for HIV infection. The fact that antisocial personality disorder and psychiatric severity are associated with risky behavior and with actual HIV infection further expands earlier findings showing that these two factors are associated with poorer treatment outcome. Other axis II disorders (e.g., borderline or narcissistic), as well as other axis I disorders with high symptom levels that were not well represented in these studies (schizophrenia, manic depressive illness), may also show similar elevated rates of risky behavior and seroconversion, although there is a scarcity of data currently available to assess the risk behavior of these patients. The evidence from treatment studies that psychiatrically focused therapies, when combined with substance abuse treatment, can improve overall outcome for patients with clinically significant levels of psychiatric symptoms may be relevant in the design of future risk reduction efforts. That is, these treatment outcome studies may serve as a starting point for exploring the feasibility and efficacy of using psychiatrically focused treatment to reduce risky behavior and HIV infection among psychiatrically symptomatic IDUs.