The BT-5 (Bystrochodnij Tankov or “Fast Tank” type 5) was an improvement on previous models. These were themselves close-copies, with specific modifications, of the US Christie M1931 “race tank”. The BT-5 shared with its predecessors the suspension, the hull (though slightly reinforced) and equipment. The turret was new, roomier and fitted for the first time with the standard 45 mm (1.77 in) gun, also used on the T-26. But this transition was not clear-cut. The BT-5 was preceded by the BT-4. Three prototypes of the latter were built in 1932 with a partially riveted, partially welded hull and modified suspension.

Like the previous model, production was assumed by KhPZ (Kharkov). Early models were provisionally fitted with an enlarged cylindrical turret (single hatch, with or without basket) and BT-2 heavy steel roadwheels. But soon after this first series, UMM instructed the design teams in Leningrad and Kharkov to adapt their model to a common turret. Thus the early model 1933 was introduced, criticized later for its awkwardly placed hatch and inadequate stowage.
The roadwheels were replaced by new, lighter convex models in 1933, which were used to upgrade the BT-2 as well. By 1934, the OKMO team had developed a better turret, with a large bustle and twin hatches, also shared with the T-26 until 1937. These were fitted to already existing vehicles . The commander tanks could be distinguished by their turret horseshoe antenna and 71-TK-1 radio set. There are still conflicting issues with the final production numbers, varying from 1884 to 2018. Steven Zaloga and most sources seem to point the former number.

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