Researchers, funders, and managers of health programs and interventions have become concerned about their long-term sustainability. However, most research about sustainability has not considered the nature of the program to be sustained. Health-related interventions may differ in their likelihood of sustainability and in the factors likely to influence continuation. I suggest a framework for analyzing the sustainability of 6 types of interventions: (1) those implemented by individual providers; (2) programs requiring coordination among multiple staff; (3) new policies, procedures, or technologies; (4) capacity or infrastructure building; (5) community partnerships or collaborations; and (6) broad-scale system change. Hypotheses for future research and strategies that program managers might use to achieve sustainability also differ by program or intervention type.