There is growing interest in the interaction between type 2 diabetes mellitus (DM) and TB, but many research questions remain unanswered. Epidemiologists, basic scientists, and clinical experts recently convened and identified priorities. This is the first of two reviews on this topic, summarizing priority areas of research regarding epidemiology, clinical management, and public health. First, from an epidemiologic point of view, more study is needed to determine the importance of transient hyperglycemia in patients with TB and on the importance of DM for the global epidemic of multidrug resistant (MDR)-TB. Second, regarding the screening and clinical management of combined TB and DM (TB-DM), clinical trials and large cohort studies should examine the benefits of improved DM care as well as prolonged or intensified TB treatment on the outcome of TB-DM and investigate the cost-effectiveness of screening methods for DM among patients newly diagnosed with TB. Third, from a public health and health systems point of view, the population health impact and cost-effectiveness of different interventions to prevent or treat DM and TB in high-burden populations should be examined, and health-system interventions should be developed for routine TB-DM screening, management of DM after completion of TB treatment, and better access to DM services worldwide. Studies are needed across different ethnicities and settings given the heterogeneity of metabolic perturbations, inflammatory responses, medications, and access to health care. Finally, studies should address interactions between TB, DM, and HIV because of the convergence of epidemics in sub-Saharan Africa and some other parts of the world.