The Birkie course is quite hilly and is recognized as one of the more difficult cross country ski marathon courses in the world, despite the fact that there are several World Loppet events in Europe that are much longer. The current north-south alignment (used since 1992) has skiers traversing a flat section before turning onto the "Powerline Hills", a series of climbs to the mark. The trail then rolls until , when Firetower Hill takes competitors to , the high point of the race and a climb of nearly from the race start. In the early years of the race, the Birkie began with a climb up the alpine slopes of Mount Telemark, mainly as a publicity stunt, but larger field sizes made this impractical. Beyond High Point is a series of downhills, including "Bobblehead Hill" or "Sledder Hill", which has a rather tricky downhill, left turn near a snowmobile trail — allowing dozens of snowmobilers to watch and "score" skiers' falls. The trail rises steeply to the crossing of County Road OO (Referred to as "Double-Oh") which, at , is the unofficial halfway point of the race. Until 2001, the Kortelopet race ended here but was rerouted back to Telemark after splitting off from the main course at . Since 2017, the Kortelopet is and begins at OO and finishes on Main Street the day before the 50km race.