The control of infectious diseases has traditionally fallen to public health and the clinical care of chronic diseases to private medicine. In New York City, however, the Department of Health and Mental Hygiene (DOHMH) has recently sought to expand its responsibilities in the oversight and management of chronic-disease care. In December 2005, in an effort to control epidemic rates of diabetes, the DOHMH began implementing a bold new plan for increased disease surveillance through electronic, laboratory-based reporting of A1C test results (a robust measure of blood-sugar levels). The controversy A1C reporting produced was relatively contained, but when Dr. Thomas Frieden, New York City health commissioner, called for the state to begin tracking viral loads and drug resistance among patients with HIV, both the medical community and a wider public took notice and have started to grapple with the meaning of expanded surveillance. In the context of the past century of medical surveillance in America, we analyze the current debates, focusing first on diabetes and then HIV. We identify the points of contention that arise from the city's proposed blend of public health surveillance, disease management, and quality improvement and suggest an approach to balancing the measures' perils and promises.