e17567 Background: Although there have been previous analyses of various aspects of studies presented at ASCO Annual Meetings, to our knowledge no attempt has been made to investigate the nationality of abstracts. Methods: After stratification into three categories of presentation ([1] oral, including plenary and all oral presentations; [2] posters, including poster discussions; and [3] publication only [PO]), we took a random sample of 10% of the abstracts from 6 years, and assigned them nationalities using authors’ affiliations. For multinational studies, we assigned nationality following an algorithm developed for the study. Importantly, we did not appraise abstract quality or results. Results: We analyzed 2,206 of the 22,045 abstracts appearing in the Proceedings and LBA Booklets for 2001–2003 and 2006–2008. Categories were oral/poster/PO in 7.8/49.2/43.0%, and study phase (as declared by authors) was I/II/III/other, unknown or not applicable in 10.8/16.5/3.3/69.4% of abstracts. There were 332 (15.0%) multinational studies, and 1,866 (85.0%) were uninational (969 multicenter, and 905 from a single institution). The top 15 countries with higher % of studies were the US (49.0%), Italy (7.5%), Japan (5.9%), Germany (5.3%), France (4.3%), Spain (3.5%), Canada (3.4%), the UK (3.3%), South Korea (1.8%), China/Hong Kong (1.4%), Brazil (1.1%), India (1.0%), Greece and Belgium (0.9% each), and Turkey (0.8%). Exploratory analyses showed a temporal increase in multinational studies (p = 0.003), no temporal trend in the proportion of abstracts with US nationality (p = 0.315), and a higher proportion of oral and poster presentations for multinational studies (p < 0.001) and for abstracts with US nationality (p < 0.001). Conclusions: This bibliometric analysis provides a geographic overview of research presented at ASCO Annual Meetings and suggests that nearly half of all abstracts are from the US, with 20% of the 71 countries represented producing nearly 90% of all abstracts accepted for the meetings. Multinational collaboration seems to be increasing in clinical cancer research. No significant financial relationships to disclose.