Background: Since 2000, a periodic count was done of members of Cochrane Review Groups (CRGs), subdivided by country of residence, using information in The Cochrane Library. Contact details are increasingly stored in ‘Archie’ (The Cochrane Collaboration’s Contact Database), so we used this for the current audit. Objective: To assess international activity within CRGs. Methods: Data were retrieved on 26 February 2009 for 24,017 contributors to CRGs, with contact details in Archie on that date. The data were analyzed by role within the CRG and country of residence, by one author (CA). Any person listed more than once was counted each time. Results: Among 52 CRGs, there were 24,017 contributors from 109 countries. This is substantially more people than previous years. Some of this increase is likely to be due to the change of source from The Cochrane Library to Archie. For comparison, there were 17,637 people (103 countries) in 2008; 13,047 (97) in 2005; and 5,436 (64) in 2000. In 2009, 18,057 (75%) contributors were listed as authors, compared with 10,698 (61%) in 2008 and similar proportions in earlier years, for example, 7543 (58%) in 2005 and 2840 (52%) in 2000. Some of the increase is due to Archie’s inclusion of authors of registered titles that have not reached the protocol stage. They are not included in The Cochrane Library. The proportion of contributors in countries with low-and middle-income economies is now 18% (4,364 contributors) of the total. It was 13% (2252 contributors) in 2008 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.