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ii Widely documented disparities in cardiovascular disease morbidity and mortality incur undue health and financial costs that compel an examination of possible mechanisms. Autonomic dysregulation, indexed with heart rate variability (HRV), is an increasingly cited mechanism underlying ethnic, sex, and social class differences in cardiovascular outcomes. The current study examines data from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Cardiac autonomic control was investigated in a sample of 849 healthy adults aged 30 to 64 years (57% female, 62 % African American, and 52 % below the poverty cut-off) who were recruited using mobile research vehicles that traveled to a probability sample of representative, diverse urban neighborhoods. Autonomic control was indexed with heart rate variability along time-domain, frequency-domain, and nonlinear complexity measures. Results suggest that African Americans, females, and younger individuals show greater cardiac vagal control than Caucasians, males, and older individuals. A profile suggestive of greater relative sympathetic activity or reduced parasympathetic activity emerges in males, particularly those of higher social class. The findings highlight a seeming conundrum of cardio-protective factors amid disparate and poorer cardiovascular outcomes in typically under-represented groups. Mechanisms underlying these differences remain to be elucidated and highlight important areas of research. ii