The story of activist group Act Up and its struggle with authority in the early years of Aids makes for a compelling and often moving documentary

"Plague!" howls screenwriter/playwright Larry Kramer like some Old Testament prophet in one of the many arresting moments from this urgent, heartbreaking, and ultimately empowering account of how Aids activists took control of their own destiny in the late 1980s when the US government and health services failed to do so. Kramer is addressing an increasingly heated Act Up (Aids Coalition to Unleash Power) meeting, silencing those who have fallen into factional bickering with a voice which conjures up rage, anger and defiance.

Kramer's outburst is extraordinary, captured in grainy footage along with 700 hours of archive material (TV interviews, news broadcasts, reportage), through which director David France sifts to put us right there in the middle of the emerging struggle. What's even more remarkable is just how effectively the disparate group Kramer calls to order manage to put aside their differences to become a dynamic and wide-ranging force for change, saving lives even as they look death in the face.

Like David Weissman and Bill Weber's equally powerful We Were Here, which movingly documented the response to the outbreak of Aids in San Francisco, How to Survive a Plague offers an enlightening portrait of community action in the face of appalling government negligence and barely concealed anti-gay prejudice. Footage of George Bush blithely advocating a "change of lifestyle" as the only cure for HIV sits alongside riotous film of Act Up members staging peaceful occupations that rattle the cages of both the government and the pharmaceutical industry.

In one gut-wrenching sequence, the ashes of lost loved ones are scattered on the lawns of the White House as baton-wielding policemen on horses attempt to prevent the protesters from making their stand (we think of Joe Hill's call to arms, "Don't mourn, organise!"). Yet even in the midst of such clashes, the authorities came to realise that, in the words of one federal official, "they know more than we do". Gradually, members of Act Up (who included scientists, chemists, and researchers) were accepted onto the boards of those struggling to oversee the crisis, their literate, informed and practical responses to floundering drug development becoming a key part of the search for a cure.

With its intimate footage of activists, several of whom fall by the wayside before the final credits, How to Survive a Plague is a compellingly watchable portrait of a battle fought under that most memorable rallying cry: "Silence = Death". Bravo.