The C101 starts on the A91 in the small village of Menstrie and heads south along Tillicoultry Road. After crossing the River Devon, the C101 continues along Menstrie Road to a large roundabout on the B9140. Continuing south along Menstrie Road, the former B9140 line, it reaches the B9096. A dogleg to the left sees the route continue along Main Street then School Road and Park Terrace, which turns sharp right to drop down to the A907 at a sharp junction just to the east of the traffic lights at Cambus. The route then continues south from those lights, through Cambus, following Station Road and Forth Road to the very end.