M2A1 (1935).

Initial production type with single fixed turret containing one .50 cal machine gun.
Seventeen units were produced.

M2A2 (1935).

Twin turrets with single M2 Browning .50 machine gun in its left turret, and an M1919A4 30.
machine gun in its right turret; the turrets partly obstructed each other limiting fields of fire.
Dubbed "Mae West".
239 units produced from 1936–37.

M2A3 (1938).

Twin turrets with two machine guns, thicker armor, slightly lengthened hull, improved engine access, increased gear ratios, better engine cooling, improved suspension, and other minor detail changes.
72 units produced.

M2A4 (1939).

Single turret with 37mm gun.
Thicker armor.
375 units produced.
Orders went to the American Car & Foundry in October 1939 upon request by the Ordnance Department.
Used in the early Pacific campaigns and training.
Only service was in Guadalcanal.
Used for training after December 1941.

M2 AT (1937)
An M2 chassis with the turret removed and replaced with a 47mm automatic gun.
The gun penetration was deemed poor and canceled in 1937.
M2A1 (1935).
Initial production type with single fixed turret containing one .50 cal machine gun. Seventeen units were produced.
M2A2 (1935).
Twin turrets with single M2 Browning .50 machine gun in its left turret, and an M1919A4 30. machine gun in its right turret; the turrets partly obstructed each other limiting fields of fire. Dubbed "Mae West". 239 units produced from 1936–37.
M2A3 (1938).
Twin turrets with two machine guns, thicker armor, slightly lengthened hull, improved engine access, increased gear ratios, better engine cooling, improved suspension, and other minor detail changes. 72 units produced.
M2A4 (1939).
Single turret with 37mm gun. Thicker armor. 375 units produced. Orders went to the American Car & Foundry in October 1939 upon request by the Ordnance Department. Used in the early Pacific campaigns and training. Only service was in Guadalcanal. Used for training after December 1941.
M2 AT (1937)
An M2 chassis with the turret removed and replaced with a 47mm automatic gun. The gun penetration was deemed poor and canceled in 1937.
M2 light tank