100 Miles of Istria is an endurance race along the Istrian hiking trail, starting from the town of Labin and finishing in Umag. The trail passes through all the Istrian hilltops as well as some urban areas.

The race consists of three categories. The longest race, which starts in Labin and ends in Umag, is 166,6 kilometres long with 6721 m of ascent and 7016 m of descent, which is equivalent to four times the rise to the top of the Učka Mountain from the sea level.
The race starts in Labin, passes through Vojak, all the way to Buzet, then turning to the interior to pass through inland gems such as Hum, Draguć, Zamask and Motovun. It then returns to its original path through Oprtalj, and on its way to Umag passes through the beautiful Završje, Grožnjan and Buje.
The time limit for completing the race is 48 hours.

The second, shorter race, starting in Lovran, passes through Vojak and Buzet to join the 100 mile race trail in Oprtalj all the way to Umag. The length of the trail is 105 kilometres and has an overall ascent of 4300 m, which corresponds to the triple ascent to the top of the Učka Mountain.
The time limit for completing the race is 33 hours.

The third race is 63,74 kilometres long and follows the medium trail all the way from Buzet to Umag. The time limit for completing this race is 18 hours.

The finish of all the races and the centre of events will be in Umag where the 1 kilometre children race will be held.

The 100 miles of Istria race is one of the qualification races for unofficial trail world championship the North Face Ultra Trail du Mont Blanc, in a way that in the longest category finishers recieve four qualifying points those in the medium category three, and those in the shortest category one qualification point.