Family caregivers of persons with bipolar disorder experience considerable stress. Yet, studies have not examined whether their stress differs by race and gender. This preliminary analysis of baseline data from 228 African American and White family caregivers of adults with bipolar disorder who were enrolled in a randomized controlled trial examined race and gender differences on two validated self-report measures of psychological stress (caregiver burden and caregiver reactions) and an electrocardiography device used to capture heart rate variability (HRV). No statistically significant differences were found by race or gender on either measure of psychological stress. African American caregivers had significantly lower scores on two indices of HRV compared to White caregivers. Women had significantly lower scores on one index of HRV compared to men. Low HRV indicates greater stress and mortality risk. Future research should include HRV to measure caregiver stress and implement relevant interventions.