Case investigation and contact tracing (CICT) is a longstanding cornerstone of public health disease control efforts for a wide array of communicable diseases, though the content of CICT varies substantially depending on the infection to which it is applied, the epidemiologic circumstances, and interventions available to control an epidemic. In this article, we discuss how CICT is currently used in public health communicable disease, sexually transmitted infection/human immunodeficiency virus, and tuberculosis control programs. We then review how CICT might be modernized, considering issues such as community and health care organization engagement, workforce development, public health program organizational structure, data information systems, case prioritization, and the content to CICT.