There are large differences in health outcomes by socioeconomic status (SES) that cannot be explained fully by traditional arguments, such as access to care or poor health behaviors. The authors consider a different explanation--better self-management of disease by the more educated, They examine differences by education in treatment adherence among patients with two illnesses, diabetes and HIV, and then assess the subsequent impact of differential adherence on health status, One unique component of this research is that for diabetes the authors combine two different surveys--one cohort study and one randomized clinical trial-that are usually used exclusively by either biomedical or/and social scientists separately. For both illnesses, they found significant effects of adherence that are much stronger among patients with high SES. After controlling for other factors, more educated HIV+ patients are more likely to adhere to therapy, and this adherence made them experience improvements in their self-reported general health. Similarly, among diabetics, the less educated were much more likely to switch treatment, which led to worsening general health. In the randomized trial setting, intensive treatment regiments that compensated for poor adherence led to better improvements in glycemic control for the less educated. Among two distinct chronic illness, the ability to maintain a better health regimen is an important independent determinant of subsequent health outcomes, This finding is robust across clinical trial and population-based settings, Because this ability varies by schooling, self-maintenance is an important reason for the steep SES gradient in health outcomes.