The Parish Walk is under way after around 1,400 walkers set off from the National Sports Centre in Douglas at 8am.
The participants are currently making their way towards their target destinations along the 85-mile course.
With such a large volume of competitors, spectators and support vehicles, a number of roads closures have been put in place.
They are: A1 Douglas to Peel Road, from 8.15am to 10.30am; Cleanagh Road, Marown/Santon, from 9am to 11.30am; Orrisdale Road, Malew, from 10am to 1.30pm; and Derby Road, Peel, from 12.30pm to 6.30pm.
A range of other routes will be one-way from 11am today (Saturday) to 7am tomorrow and motorists are asked to drive and park with consideration and patience.
The iomtoday sports team will be providing updates throughout the day on their Twitter account @iomsportsdesk
To follow individual walkers, click the following link to the Manx Telecom Parish Walk live timing page and enter their name see how they’re getting on: parishtiming.manxtelecom.com/
To read a full preview, click here: Richard Gerrard starts as favourite to win Parish Walk
Road closure and one-way information from the Department of Infrastructure: http://www.gov.im/residents/roadnotifications/Notification.aspx?id=4813