Schizophrenia and bipolar disorder have high rates of medical comorbidity, in particular obesity, diabetes, and cardiovascular disorders. This investigation assessed (a) patient awareness of comorbidities associated with their mental illness, (b) patient knowledge of long-term health risks associated with mental illness and its treatment, and (c) interaction with health care providers regarding comorbid conditions. An Internet-based survey of patients currently receiving pharmacotherapy for schizophrenia or bipolar disorder was conducted in 11 countries. The following results are from a US sample of 135 patients with schizophrenia and 135 with bipolar disorder. Among subjects with schizophrenia, 29% self-reported obesity, 32% diabetes, 28% hypertension, and 18% other cardiovascular disease. Similarly, 29% of patients with bipolar disorder reported obesity, 14% diabetes, 21% hypertension, and 8% other cardiovascular disease. A BMI >30 kg/m2 was reported in 71% of subjects with schizophrenia and 51% of subjects with bipolar disorder. Health care providers discussed potential long-term consequences of weight gain with 61% of subjects with schizophrenia and 42% of subjects with bipolar disorder, and they discussed the impact of psychotropic medication on comorbidities with 60% of subjects with schizophrenia and 40% of subjects with bipolar disorder. However, only 20% of subjects with schizophrenia and 24% of subjects with bipolar disorder reported receiving a physical examination, 35% and 42% respectively reported being weighed, and 28% and 36% respectively reported having a blood test. These results suggest that subjects in this sample are suboptimally informed about issues surrounding comorbidity and its long-term consequences despite high rates of medical comorbidity.