A reposable endoscopic surgical clip applier, comprising: a handle assembly, including: a housing including a stationary handle and a barrel supported on the stationary handle, the barrel including a proximal end, a distal end, and a longitudinal axis, the barrel defining a lumen extending between the proximal and distal ends thereof, the lumen aligned on the longitudinal axis and including a proximal portion and a distal portion; a trigger operably coupled to the housing and movable relative to the stationary handle from an un-actuated position to an actuated position; a plunger assembly removably positionable within the proximal portion of the lumen, the plunger assembly including a plunger having a head and a shaft extending distally from the head and being configured to operably couple to the trigger such that movement of the trigger from the un-actuated position to the actuated position advances the plunger assembly distally though the proximal portion of the lumen; and a plug removably engagable within the proximal end of the barrel to close off the proximal portion of the lumen, thereby retaining the trigger in operable relation relative to the plunger assembly; the clip applier further comprising a plurality of adapter assemblies (400, 500), each of which is operably associated with at least one of: a clip cartridge assembly, an end effector, or a surgical tool, characterized in that at least one of the adapter assemblies includes: an outer shell; a collar slidably disposed within the outer shell; a shaft engaged with the collar and extending distally from the collar and the outer shell; and a plunger assembly slidably disposed within the outer shell, the plunger assembly including a stem and a plunger slidable relative to the stem, the plunger including a head and a shaft extending distally from the head, wherein each adapter assembly is configured for releasable receipt with the distal portion of the lumen in operable relation relative to the plunger assembly of the handle assembly such that distal movement of the plunger of the handle assembly urges the plunger of the at least one adapter assembly distally to actuate the clip cartridge assembly, end effector, or surgical tool associated with that adapter assembly. a handle assembly, including: a housing including a stationary handle and a barrel supported on the stationary handle, the barrel including a proximal end, a distal end, and a longitudinal axis, the barrel defining a lumen extending between the proximal and distal ends thereof, the lumen aligned on the longitudinal axis and including a proximal portion and a distal portion; a housing including a stationary handle and a barrel supported on the stationary handle, the barrel including a proximal end, a distal end, and a longitudinal axis, the barrel defining a lumen extending between the proximal and distal ends thereof, the lumen aligned on the longitudinal axis and including a proximal portion and a distal portion; a trigger operably coupled to the housing and movable relative to the stationary handle from an un-actuated position to an actuated position; a plunger assembly removably positionable within the proximal portion of the lumen, the plunger assembly including a plunger having a head and a shaft extending distally from the head and being configured to operably couple to the trigger such that movement of the trigger from the un-actuated position to the actuated position advances the plunger assembly distally though the proximal portion of the lumen; and a plug removably engagable within the proximal end of the barrel to close off the proximal portion of the lumen, thereby retaining the trigger in operable relation relative to the plunger assembly; the clip applier further comprising a plurality of adapter assemblies (400, 500), each of which is operably associated with at least one of: a clip cartridge assembly, an end effector, or a surgical tool, characterized in that at least one of the adapter assemblies includes: an outer shell; a collar slidably disposed within the outer shell; a shaft engaged with the collar and extending distally from the collar and the outer shell; and a plunger assembly slidably disposed within the outer shell, the plunger assembly including a stem and a plunger slidable relative to the stem, the plunger including a head and a shaft extending distally from the head, wherein each adapter assembly is configured for releasable receipt with the distal portion of the lumen in operable relation relative to the plunger assembly of the handle assembly such that distal movement of the plunger of the handle assembly urges the plunger of the at least one adapter assembly distally to actuate the clip cartridge assembly, end effector, or surgical tool associated with that adapter assembly. an outer shell; a collar slidably disposed within the outer shell; a shaft engaged with the collar and extending distally from the collar and the outer shell; and a plunger assembly slidably disposed within the outer shell, the plunger assembly including a stem and a plunger slidable relative to the stem, the plunger including a head and a shaft extending distally from the head, wherein each adapter assembly is configured for releasable receipt with the distal portion of the lumen in operable relation relative to the plunger assembly of the handle assembly such that distal movement of the plunger of the handle assembly urges the plunger of the at least one adapter assembly distally to actuate the clip cartridge assembly, end effector, or surgical tool associated with that adapter assembly.