All trains were powered by diesel locomotives, the last steam locomotive having been consigned to a museum in the 1970s. Freight cars were of Soviet manufacture, and passenger cars were imported from East Germany. More than 90 percent of all railroad freight was loaded and unloaded by mechanized means.

In the late 1980s, Mongolia had 1,750 kilometers of 1.524- meter, broad-gauge track. Major lines included the Ulaanbaatar Railroad, which connected Ulaanbaatar with Suhbaatar and Naushki, Soviet Union, in the north, and with Dzamyi Uud, Mongolia, and Erenhot, China, in the south. The eastern line connected Choybalsan with Ereentsav, Mongolia, and Borzya, Soviet Union. Another line linked the Trans-Siberian Railway with Beijing. Branch lines ran from Darhan to the Sharin Gol coalfield from Salhit, near Darhan, to Erdenet from Bagahangay to the Baga Nuur coal mine and from Har-Ayrag to the Bor Ondor fluorite mines. Mongolia's railroad company, Ulaanbaatar Railroad, was a jointstock venture with the Soviet Union both countries had equal shares in the company. The director was Soviet the deputy director and the chairman of the board were Mongolian. In 1985 Ulaanbaatar Railroad carried 14.8 million tons of freight and 5,822.8 million ton-kilometers of freight turnover, accounting for 75 percent of all freight turnover. In 1985 the railroad transported 2.1 million passengers and accounted for 432.2 million passenger-kilometers, or 30.6 percent of all passenger turnover. Railroads also accounted for 97 to 98 percent of all import-export transportation. Each year Mongolia signed a multilateral railroad transportation protocol governing importexport freight transport with the Soviet Union, China, and North Korea.

Data as of June 1989