Background: The mortality due to cardiovascular diseases in bipolar patients is much higher than in the general population. It is unclear whether lithium treatment contributes to this cardiovascular morbidity. Methods: The cardiovascular risk factors in outpatients with bipolar disorder on monotherapy lithium were explored. Cardiac (family) history, important habits and recent stressful events were assessed. Quetelet Index (QI) was calculated and blood samples were taken. Blood pressure (BP) was measured in supine position and during orthostatic challenge. Results: 40 out of 81 patients on monotherapy lithium were studied in detail. In this group, one patient was hypothyroid; six patients suffered from hypertension. QI was > 25 in 57.5% of the patients; mean cholesterol level was 5.7 mmol/L. Renal functioning, electrolytes and glucose concentrations were normal. There were no significant relationships between the duration of lithium treatment, the duration of bipolar disorder, recent stressful events and hypertension. Out of the group of 81 patients on lithium monotherapy, 13 patients in total used antihypertensive medication, indicating a high prevalence of hypertension in this group as compared to the general population. Conclusions: Cardiovascular risk factors, including hypertension, were increased in a large proportion of this population on monotherapy lithium. However, no significant relationships were observed between duration of lithium treatment or bipolar disorder and presence of hypertension.