Mesoscopic metal rings can carry persistent currents driven by a constant magnetic field. The geometrical structure of a toroidal carbon nanotube can be characterized by four independent parameters. We derive the formula for persistent currents driven by a constant Bohm--Aharonov type of field perpendicular to the plane of the torus. The dependencies of the currents on the chirality, twist and circumference of the torus are discussed.

PACS numbers: 03.75.Fi