Active duty refers to a full-time occupation as part a military force, as opposed to reserve duty.

Israel

In the Israel Defense Forces, there are two types of active duty: regular service (, Sherut Sadir), and active reserve duty ( Sherut Milu'im Pa'il, abbr. Shamap). Regular service refers to either mandatory service (, Sherut Hova), according to the laws of Israel, or standing army service (, Sherut Keva), which consists of paid NCOs and officers.

Active reserve service refers to the actual time in which reservists are called up. This varies from once every few years to a month every year. During active reserve duty, military law can be applied to reservists, similarly to regular soldiers.

United States

In the United States military, active duty refers to military members who are currently serving full time in their military capacity. Members of a reserve component are not generally considered active duty. However, in support of the Global War on Terror and other contingency operations, a large number of Reservists in all branches have been called to active duty in an operational capacity. Many will argue that today's Reserve forces are no longer the "strategic" Reserve of the Cold War. It is widely accepted that today's Reserve components have become operational entities that play a key role in all of the Nation's conflicts. Those Reservists deployed in support of contingency operations, either as a unit or by individual augmentation, are also considered active duty. These terms may also be applied to military forces of other nations, although the details concerning obligations to serve may differ.