Background: Since 2000, a periodic count has been done of members of Cochrane Review Groups (CRGs), subdivided by country of residence. Initially, this used data from The Cochrane Library but for the audits in 2009 and 2010, it used Archie (The Cochrane Collaboration s Contact Database). Objective: To assess international activity within CRGs. Methods: Data were retrieved on 9 February 2010 for all contributors to CRGs whose contact details were in Archie. One author (CA) analyzed the data by role within the CRG and country of residence. People listed more than once were counted each time. Results: Among 51 CRGs, there were 27,724 contributors from 110 countries. There were 17,637 people (103 countries) in 2008; 13,047 (97) in 2005; and 5436 (64) in 2000.The substantial increase in the recorded number of contributors over the past two years is due in part to the change of data source from The Cochrane Library to Archie. In 2010, 21,122 (76%) contributors were listed as authors, compared with 18,057 (75%) in 2009; 10,698 (61%) in 2008 and similar proportions in earlier years (e.g. 7543 (58%) in 2005 and 2840 (52%) in 2000). Some of the increase since 2008 is due to Archie s inclusion of authors of registered titles that have not reached the protocol stage (these were not included in The Cochrane Library). There are now 5315 contributors in countries with low- and lowermiddle, and upper-middle income economies (19% of the total), compared to 18% (4364 contributors) in 2009 and 6% (307) in 2000. Conclusions: The number of people involved in the work of The Cochrane Collaboration continues to grow, as does its international diversity. There is a continuing increase in contributors from low- and middle-income countries. Other data analysis will be shown in the poster. The data are available at www.cochrane.org.