They were used throughout the GWR system where the gauge permitted; principally in the Northern Division to start with.

Six of the class were sent to Serbia in 1916, two of them returning in 1921; and 16 of them were shipped to Salonika in 1917, though the first batch of eight was lost at sea.

After the war four of them entered the stock of the Ottoman Railway; another four were returned to the GWR in 1921.

The 388 class were built in several batches between 1866 and 1876; many locomotives were given numbers from recently withdrawn locomotives, so they do not run in a continuous series, or even in order of construction.

1100 was struck by a broad gauge boat train from Plymouth at Norton Fitzwarren.