The Type 99 self-propelled howitzer was developed as a replacement to the Type 75 SPH. It was developed by the Mitsubishi Heavy Industries and the Japan Steel Works. A small number of Type 99 self-propelled howitzers is currently in service with the Japanese Ground Self-Defense Force. It has not been offered for export customers, as Japan's laws do not allow exporting military equipment.

The Type 99 self-propelled howitzer is fitted with 155-mm howitzer, which is believed to be 39 calibers long. Maximum range of fire is 30 km with standard HE-FRAG projectile and approximately 38 km with rocket assisted. Maximum rate of fire is speculated to be 6 rounds per minute.

Secondary armament of the Type 99 consists of a roof-mounted 12.7-mm machine gun, fitted with a shield.

Armor of the Type 99 provides protection against small arms fire and artillery shell splinters.

Vehicle is powered by a diesel engine, developing 600 horsepower. A traveling lock is provided at the front of the hull. It folds back onto the glacis plate when not in use.

The Type 99 self-propelled howitzer is resupplied from the Type 99 ammunition resupply vehicle.

In the FY00 defence budget, the Japanese Defence Agency revealed that it was to procure seven Type 99 155 mm self-propelled howitzers for the Japanese Ground Self-Defence Force.

It is understood that the Type 99 had been under development for some years under the leadership of Mitsubishi Heavy Industries (hull and final assembly) and the Japan Steel Works (gun and turret system).

The Type 99 155 mm self-propelled howitzer is the replacement to the older 155 mm Type 75 self-propelled howitzer. It is known that four Type 99 155 mm self-propelled howitzers were procured in 1999. The Type 99 is now operational with the Japanese Ground Self-Defence Force.

A total of seven Type 99 155 mm self-propelled systems were ordered in FY00 with a further six ordered in FY01. Like all other post-1945 Japanese armoured vehicles and artillery systems, the Type 99 155 mm self-propelled howitzer has not been offered on the export market.

A total of eight were funded in FY03 and a further eight in FY04.

The overall layout of the Type 99 155 mm self-propelled gun is similar to other recent weapons of this type.

The driver is seated at the front right with a single-piece hatch cover above his position and forward of these are three day periscopes, the centre one of which can be replaced by a passive periscope for driving at night.

The power pack, consisting of diesel engine, transmission and cooling system is mounted to the left of the driver, with the air inlet and outlet louvres in the roof and the exhaust outlet in the left side of the hull.

The fighting compartment is at the rear with normal means of entry and exit for the crew via a door in the lower part of the hull rear.

The fully enclosed turret is at the rear with the commander seated on the right side and provided with a roof-mounted .50 (12.7 mm) M2 HB MG machine gun mount that is also fitted with a shield.

In addition to the roof hatches there is also a single door in either side of the turret. The one on the left side opens to the rear while the one on the right side opens to the front.

The 155 mm ordnance, which is believed to be a 39 calibre weapon, is provided with a muzzle brake but no fume extractor. A travelling lock is provided at the front of the hull and when not in use, this folds back onto the glacis plate. It is understood that the ordnance is based on that used in the towed FH-70 155 mm towed artillery system, which has been manufactured under licence in Japan for some years. Maximum stated range of the Type 99 is quoted at 30,000 m.

It is considered probable that some type of automatic loading system is provided and mounted over the rear part of the ordnance in what appears to be a muzzle velocity measuring device. This would feed information into the onboard fire-control system.

Suspension either side consists of seven dual rubber-tyred road wheels with the drive sprocket at the front, idler at the rear and track return rollers.

Standard equipment includes a NBC system and passive night driving aids.