Pz.Kpfw.III (Sd.Kfz.141) was intended to be the anti-tank vehicle of the tank tandem envisioned for Germany's developing tank divisions. The tank was armed with a 3.7cm gun in deference to logistics; the standard infantry AT gun at the time was the 3.7cm weapon, however the troops wanted a 5cm gun instead, so turret ring was designed to be large enough to allow later up-gunning.

Ausfuehrung B (Sd.Kfz.141) ran on a different suspension consisting of eight dual road wheels per track, in four bogies, sprung by one leaf spring per bogie. The commander's cupola also was changed, as well as the engine louvres on the rear deck.

Pz.Kpfw.III Ausf.C (Sd.Kfz.141) again modified the running gear, with the first and last road wheel bogies sprung by their own leaf springs, while the center pair of bogies shared a larger leaf spring. Ausf.C also featured modified drive sprocket and idler wheels.

Ausfuehrung E (Sd.Kfz.141) was the first real production model, and ran on torsion bars, which would be the standard suspension for the rest of the series. The hull sides were now made of single plates which featured escape hatches for the driver and radio operator. Starting in August 1940, tanks were upgunned to take the 42-caliber 5cm gun, and 30mm spaced armor plates were bolted to the hull front and rear. The new gun was held in an external gun mantlet, compared to the 3.7cm gun's internal mantlet.

Ausf.F (Sd.Kfz.141) featured a new ignition system, and cast air intakes were added to the hull front to cool the tank's brakes. About one hundred Ausf.F were built with the 42-caliber 5cm gun, and more were upgunned after they had been built. Thirty millimeter armor plate was also added to the Ausf.F.

Most Pz.Kpfw.III Ausf.G (Sd.Kfz.141) were armed with the 5cm gun; only about the first fifty produced were built with the 3.7cm gun, and most of these were upgunned later. The driver's visor was changed to a pivoting model instead of the earlier sliding visor. The turret was lengthened to engulf the commander's cupola; previously, the cupola had emerged from the turret rear plate.

Ausfuehrung H (Sd.Kfz.141) was armed with the 5cm gun from the start, and the additional armor plate was bolted to new production vehicles. The turret rear was redesigned as a single plate, and the drive sprocket and idler wheels were changed to a spoked design. The position of the front return roller was changed to place it closer to the drive sprocket to lessen pressure and wear on the sprockets. A turret basket was introduced on this tank, and these were subsequently fitted to earlier tanks.

The base armor of Ausf.J (Sd.Kfz.141) was increased to 50mm, necessitating a new driver's visor (Fahrersehklappe 50), bow machine gun mount (Kugelblende 50), and brake cooling air intakes. The split access hatches in the hull front of earlier tanks were replaced with single-piece, front-hinged models. The towing hooks were also modified on Ausf.J: previously, the hooks had been bolted to the hull, but on Ausf.J the hull sides were lengthened and the towing eyes were formed from the hull side plates. Starting in December 1941, the long 5cm Kw.K.39 L/60 was introduced to the second Ausf.J series (Sd.Kfz.141/1), and 1067 of the 2616 Ausf.J built were armed with the longer weapon. The new weapon limited ammunition stowage to eighty-four 5cm rounds. Twenty millimeter armor plates were added to the gun mantlet and superstructure front starting in April 1942. A stowage bin was added to the turret rear, and retrofitted to earlier tanks. During the production run, the loader's mantlet vision port and side turret vision ports were eliminated.

The turret front was uparmored on Ausf.L (Sd.Kfz.141/1), the engine air intakes were again modified, and the main weapon received a torsion bar counterbalance instead of the earlier helical spring. The driver's and radio operator's escape hatches were deleted during production, and this allowed an increase in ammunition stowage.