Despite a high prevalence of HIV in patients with serious mental health disorders, there is little information in the literature regarding details of their HIV treatment. The objective of this paper is to assess factors associated with the success of HIV therapy in people with schizophrenia, schizoaffective, and bipolar disease. The methods used are retrospective, post-study chart review, and clinician questionnaire at two HIV county clinics. Forty-nine (4.8%) study patients were identified, 51% of whom achieved an undetectable HIV viral load. These patients tended to have less drug use (42% vs. 68%), more ongoing psychiatric visits (70% vs. 58%) and were more apt to take psychiatric medicines (70% vs. 40%) than patients with detectable HIV viral loads. Both groups had many missed appointments. We were surprised to find that many patients were successful with HIV treatment despite substance abuse, uncontrolled psychiatric symptoms, and lack of psychiatric care. Missing clinic appointments had little influence on treatment outcome.