Around 7,000 people are expected to run the Leeds Half Marathon which has been organised for the second time by Jane Tomlinson's Run For All.
An extra thousand places were made available after the original allocation filled, and organisers are expecting it to be the biggest hospice run of its kind.
Last year's event raised around £150,000 for charities.
As well as the half-marathon, a Corporate Relay, and a Mini and Junior run for 1,500 children will also take place.
More than 1,000 walkers stepped out for Jane Tomlinson's Yorkshire Dales Walking Festival this morning.
The walk, which features four routes - 28 miles, 14 miles and five miles, will raise tens of thousands of pounds for causes close to people's hearts.
This third Yorkshire Dales Walking Festival set off earlier from Settle and will take in sights like Malham Cove, Fountain's Fell and Pen-y-Ghent.
Thousands of runners have taken part in Jane Tomlinson's Run For All in York. The race, started by Jane's husband Mike, set off this morning from the Knavesmire at the city's racecourse.
The 10 kilometre route saw runners pass through the centre of York, the first crossing the finishing line in just over 30 minutes.
More from the Leeds 10K, which was started off by Calendar's very own Christine Talbot and Duncan Wood, who also took part.
One of the biggest 10k races in Yorkshire has got underway.
The Asda Foundation Leeds 10K, organised by Jane Tomlinson's Run For All - began at 9.30am - on one of the warmest days of the year, with the temperature expected to stay around 24 degrees.
Up to 10,000 runners are currently pounding the pavement, doing the new route, designed to be flatter and faster than in previous years.
In its seventh year, the event launched by the late Jane Tomlinson CBE has so far raised more than £2m for charity.
Former England and Leeds United player Danny Mills is encouraging people to sign up for Run For All 10k events in Yorkshire.
The 10k events are part of the legacy of the late Jane Tomlinson CBE who raised almost £2m for charity by taking part in a series of incredible physical challenges, despite suffering from incurable cancer.
Danny said: “Jane Tomlinson was such an inspiration to so many people – me included. The 10Ks are part of her enduring legacy and I hope people are encouraged to take part in these fantastic events this Spring and summer.
"I’ve run the Leeds 10K a few times and I’m running again this year. The atmosphere is like nothing else and I’m really looking forward to it.”
This year's Jane Tomlinson 10k run in Leeds has had a massive revamp- with a new route and carnival feel. The course promises to be flatter and faster and runners will be entertained to help spur them on as Lisa Walton reports.
The new route for the Leeds 10k run, has been revealed today. Launched by the inspirational Jane Tomlinson in 2007, organisers say the race will be flatter and faster for 2013. It will start and finish in Leeds city centre and take in some of the city's most iconic landmarks.
It begins near the Grand Arcade in Vicar Lane and will go down through The Calls, past City Square and the famous Black Prince statue, along Wellington Street and onto Kirkstall Road
It then loops back on itself, bringing race goers back towards the Headrow for the grand finish outside Leeds Town Hall.
For more information click here.
The legacy of fundraiser Jane Tomlinson has been remembered once more at a new awards ceremony in Leeds.
Ashley Jackson has completed his tribute to Jane Tomlinson, a painting of Pen-y-ghent in the Yorkshire Dales, to be auctioned off for charity. He started the painting at the launch of the Jane Tomlinson Walk for All earlier this month.