The class 99 was designed by Karl Gölsdorf for use on secondary lines, for example where single through coaches had to be hauled with sufficient speed. It was introduced in 1897 and like many Austrian locomotives of that time, it was a two-cylinder compound with two interconnected domes. The cylinders were mounted between the leading and the first driving axle, what improved the running characteristics.
By 1908, 69 had been built for the kkStB. Five more were delivered to the NÖLB between 1903 and 1907 and designated class 2. They could easily exceed the required output of 300 hp and could even reach 400 hp when running on good coal. Even climbing inclines of up to five percent, they could be found in many corners of the empire.
For South Tyrol, the class 199 was designed with larger supplies. In comparison to the 99, it could carry 6,000 litres of water and 2,100 kg of coal, instead of 4,800 litres and 1,250 kg. The kkStB got 20 of these between 1908 and 1913, and also the NÖLB ordered nine more of the same type which became their class 102. Only two superheated compounds were built as class 299. Again the NÖLB ordered three of these superheated locomotives as their class 202, but these had simple expansion.
After World War I, the BBÖ had only 34 left which were joined by 18 from the NÖLB when this was nationalized. The largest foreign operator was the ČSD with 34 which were designated class 320.0. 13 became JDŽ class 153, eight became FS classes 876 and 877 and the two class 299 locomotives became CFR class 299. From 1938, the Reichsbahn numbered the BBÖ classes 99 and 199 as class 9813. The ÖBB designated them classes 91, 91.1 and 191 from 1953 and retired the last one in 1972. Today two are still surviving in Austria, with 91.107 in operational condition. Three more can be found in Slovenia.