The scouting movement celebrated its 100th anniversary in 2007
The number of scouts in the UK has increased by 16,500 since the start of 2009, the biggest growth in 38 years, according to figures.
Membership has now risen for five years in a row, taking levels to nearly 500,000, the Scout Association said.
The surge was largely due to a record level of interest from teenagers, who now number more than 65,000, it said.
But it warned the need for more adult volunteers meant waiting lists to join the movement were at an all-time high.
Although more than 13,500 new scouting places have been created this year thanks to 2,871 new adult volunteers - up 3.1% on 2009 - some 33,500 young people are still waiting to join, it said.
The number of teenage members has risen more than 26% since 2001.
Adventurer Bear Grylls, 35, who is the UK's chief scout, said the surge in scouting was "fantastic".
"Scouting is empowering, wild and fun, and offers so many adventure-based activities for young people and adults alike.
"My goal is for every young person that wants to be involved in scouting to be able to be so I hope to inspire even more adults to volunteer and help this happen," he said.