The deadline for taking part in the 4th Llangollen Round Challenge in aid of Cancer Research UK is midnight on Sunday May 8, say organisers.
Around 500 people from across the UK are expected to take part in the sponsored 35-mile hike which is being held over two days on May 28 and 29.
A spokesperson for the challenge said: "We are fast approaching the entry limit for the 2022 Llangollen Round Challenge, so sadly booking must close at midnight on Sunday.
"Make sure you let any friends know not to leave it too late."
The spokesperson added: "We'll promise you magnificent scenery along the way and support in completing the course.
"The route will be waymarked and marshalled, with five checkpoints carrying water and light refreshments. Back at base there will be more food, certificates and medals for everyone.
"In line with last year we expect around 500 entrants."
* For more information about how to take part in the challenge, call Judy on 07905 330788, or visit the Llangollen Round Facebook page at: https://www.facebook.com/llangollenround2022