It connects Portet-sur-Garonne, 11 km south of Toulouse on the Toulouse–Bayonne railway, to Latour-de-Carol and Puigcerdà, towns located on each side of the French/Spanish border in Cerdanya.

The service between Latour-de-Carol and Puigcerdà and onwards to Barcelona is provided by the Spanish Railway (RENFE) for which the gauge is 1,668 mm (5 ft 5+21⁄32 in).

Note that this line is a section of a railway between Toulouse and Barcelona requiring a change of train at Latour-de-Carol and a journey of 7:00hrs between the two cities, but it avoids, having to use the much more expensive trains such as the AVE (via Perpignan, a route not requiring any changes).

The railway was built by the Compagnie des Chemins de fer du Midi.

The direct connection Latour-de-Carol to Paris is provided by the Intercités de nuit night train.