The northern segment begins as a continuation of State Highway 87 near the extreme southeastern corner of Oklahoma.

The southern segment begins 13 miles (21 km) to the south along US 59 / US 71, at the Texas state line.

South of Alleene, the route intersects Highway 234 at a four-way stop.

The southern segment of Highway 108, in Miller County, serves as a northern bypass of Texarkana.

Its eastern terminus is at an intersection with Highway 41 1 mile (1.6 km) south of Foreman.