Some 2000 groups are estimated to be producing work, while in Scotland, the Scottish Community Drama Association (SCDA) is a major hub of am dram activity.
Some of the best am dram groups are currently on show in Nation's Best Am Dram, a six part TV series on Sky Arts HD, which pits teams against each other in a competition judged and mentored by high-profile theatre professionals. With three very different Scottish groups making it down to the last eight, and with performance in a London West End the prize for the winner, am dram is a very serious business for everyone involved.
By way of actor and director Kathy Burke's throaty narration, the first two episodes of Nation's Best Am Dram have introduced viewers to Edinburgh Graduate Theatre Group (EGTG), the Glasgow-based Strathclyde Theatre Group (STG) and, from Castle Douglas in Galloway, Crossmichael Theatre Group. STG and Crossmichael were selected along with another five from video submissions judged by actor Miriam Margolyes and critic Quentin Letts, with producer Bill Kenwright chairing the panel. In a spirit of democracy, EGTC were selected by the public.
"We've always seen that as a positive," says David Grimes, a lawyer and EGTG's director. "At the end of the day it's the public buying the tickets, so obviously they saw something that the judges missed first time round."
For the quarter finals, half of the competitors were tasked to present a scene from Ibsen's An Enemy of the People, while the other half had to do likewise with a scene from Chekhov's The Cherry Orchard. After three weeks rehearsals, each company was assigned a professional mentor, who appraised their progress while offering advice.
While EGTG were looked after by former Heartbeat star and National Theatre regular Niamh Cusack, STG were watched over by Royal Shakespeare Company stalwart Dame Harriet Walter. Crossmichael, meanwhile, found Peep Show star Paterson Joseph, another RSC regular, making the trek to Galloway to work with them.
"He worked us really hard," says Crossmichael director and full-time carer Anne McIntyre. "I do farce and comedy. That's my thing, and I tend to move people around all the time, but Paterson taught me the importance of being still."
STG, too, are full of praise for their mentor.
"It was wonderful to have such an experienced actor as Dame Harriet Walter to help us," says STG director Bruce Downie. "She took a lot of time to work with people individually, and that made an invaluable difference."
Grimes describes Cusack as "absolutely the best mentor. She changed what we did completely, and it was so enlightening to see her process.
"There's a running joke now when we're rehearsing something, and someone will say, 'How would Niamh do it?'"
For Cusack herself, Nation's Best Am Dram was something of an eye-opener.
"It's making people interested in theatre," she says. "Am dram is a social thing as much as anything. It allows people to use their imagination and broadens people's lives, and I think it's important that people all over the country, especially in areas which perhaps don't have access to professional theatre, are getting up and doing it for themselves."
"Am dram forms communities," she says, "and it allows people to have some kind of creative release beyond the rest of their lives. A programme like this might make people watching it think, 'That could be me up there.'"
In the third episode of Nation's Am Dram, shown tomorrow, viewers will be able to see Cusack put STG and EGTG through their paces with The Cherry Orchard. Walter will be seen doing likewise with STG, who are forced to make a last-minute cast change. Best of all in this week's programme is Richard Wilson's response to one group's reimagining of The Cherry Orchard in a sanatorium peopled by delusional patients.
How, though, have the groups fared since the series was filmed more than a year ago?
Since Nation's Am Dram ended, STG have been forced to vacate their home at the Strathclyde University owned Ramshorn Theatre, but the company is still going strong and have just completed a run of Arthur Miller's Death of A Salesman directed by Downie at Cottiers Theatre.
"It's been a difficult 18 months," says Downie. "We lost what had been our home for the past 20 years, and a lot of members drifted away, but the competition came along at exactly the right time. It regenerated focus for the group and I think gave people a new sense of purpose."
EGTG remain similarly galvanised, and this year alone have put on productions of Doctor Faustus and Jez Butterworth's play, Jerusalem, while only last week they staged Shakespeare's Richard III.
"We do four shows a year, anyway," says Grimes, "so even while filming, we were rehearsing for our next production at the same time."
For Crossmichael, whose members are more geographically spread out than STG and the Edinburgh Grads, the experience has been very different.
"We usually only do festivals between January and March," says McIntyre, "so we haven't really met much recently. By the end of this, having spent so much time together, I think we'd been in each other's company too long, but we've met to choose a script for the SCDA, and now it's back to business as usual. We were talking about putting something on at the [Edinburgh Festival] Fringe this year. If there's any year we're going to do it, this has to be the one."
Nation's Best Am Dram, Sky Arts HD, Wednesdays at 9pm www.sky.com/arts