After the Second World War, the Belgian State Railways were looking for electric locomotives suitable for series production. On the one hand, the Type 101 was procured, which was based on series models already used in France, and the Type 121, which was developed in Switzerland and built in Belgium with some components from Switzerland. On the other hand, three independent locomotives were developed and built by the Belgian company Baume & Marpent. These were designated Type 120 and were used in regular service from 1950.

It was a contemporary design with a cuboid but slightly rounded body, four individually powered axles and no carrying axles. These were designed for the 3,000 volt DC system used in Belgium, which had been in place since 1935 and would expand in the post-war period. The produced quantity stagnated at three, these were delivered in two shades of green and later got yellow stripes on the fronts to increase visibility. The locomotives became the HLE 20 in 1971 and just two years later they were again redesignated the HLE 28 in favor of a new class. They spent their final years shunting empty passenger trains for Brussels Midi station and were retired by 1996. Today the number 28 is used by a variant of the Bombardier TRAXX.

The first electric locomotives to be procured in large numbers in post-war Belgium were the later HLE 22, 23 and 25. These were four-axle locomotives with a top speed of 130 km/h, an hourly output of 1,880 kW and a continuous output of 1,740 kW. The original version was the type 122, of which 50 examples were built between 1953 and 1954. Initially, they were only designed for 3,000 volts direct current and had ventilation grilles in the roof area, which later turned out to be problematic with regard to the ingress of rain. They were designated as Series 22 in the new numbering scheme of 1971.

Due to the problems with the arrangement of the ventilation grilles, the type 123 was built between 1955 and 1957, in which the grilles were arranged in the lower area of the side walls. Since these locomotives were also intended to pull heavier freight trains, the weight was increased by five tonnes. After 83 examples of the 123, further examples were built in 1960 and 1961, which were again three tonnes lighter than the type 122. These were 16 of the type 125 and six of the type 140. The latter were distinguished by the fact that they were designed for 140 km/h with another gear ratio. Since the ten additional km/h did not pay off considering the loss of tractive power, this was converted to 130 km/h and classified as type 125. From 1971 the types 123 and 125 became the HLE 23 and 25.

In 1971, an HLE 23 locomotive was fitted with a streamlined paneling on one side and was operated at up to 200 km/h in test runs. Other HLE 23 locomotives were later equipped for multiple working and were then often found in pairs in front of freight trains. Eight examples of the HLE 25 were equipped in the 1970s as the first Belgian locomotives for push-pull operation with one locomotive at each end of the train. They were designated HLE 25.5 and were later partly superseded by newly built control cars at one end of the train. Some of the HLE 23, 25 and 25.5 locomotives were also adapted for operation under 1,500 volts DC in the Netherlands. In the 21st century, the locomotives were mostly only used for freight trains. In 2009, most examples were still in service but then faced rapid retirement and the last examples of the 25.5 disappeared in 2012.

The class 71, initially known as the type HA, was a locomotive for third rail electrified lines. Depending on the region, they were operated with 650 or 750 volts. For station areas with many points, in which there was an overhead line instead of the third rail, they had a pantograph on the center roof. To overcome short non-electrified gaps, they had a flywheel to maintain speed. Nevertheless, the first ten locomotives were converted to diesel locomotives as early as the 1960s because they had competition from the class 73 electro-diesel locomotives. The latter ultimately led to all remaining locomotives being withdrawn at the same time in 1977.