The International Cochrane Collaboration is two years old. From small beginnings in September 1992 its membership has grown to over 1000 people. It now has eight collaborating centres around the world and international review groups dealing with 30 clinical areas. Its second international meeting last week in Hamilton, Ontario, attracted over 400 people from 20 countries. But despite these signs of success many who could benefit from the collaboration's work, or contribute to it, remain unaware or unsure of its purpose.

Named after the British epidemiologist Archie Cochrane, the collaboration was set up to evaluate the available evidence from randomised controlled trials. Its underlying assumption is that health care interventions will be more effective if they are based on complete and up to date evidence instead of out of date research, anecdote, and conjecture. Its eventual goals are to create a register of all completed and continuing randomised controlled trials; to combine the results of trials that meet set standards of quality; to produce regularly updated systematic reviews or meta-analyses; and to make these reviews widely available in journals, on CD-ROM, and eventually on line through the internet.

With sophisticated computerised databases such as Medline, finding all randomised …