Table 1 Characteristics of large randomized trials registered with ClinicalTrials.gov prior to 2009. Values are numbers (percentages) unless stated otherwise

Trial characteristicsAll trials (n=585)Published trials (n=414)Unpublished trials (n=171)
Mean (SD) No of participants1693 (5580)1668 (3217)1753 (9045)
Trial phase*:
 I/II84 (14)43 (10)41 (24)
 III394 (67)290 (70)104 (61)
 IV58 (10)40 (10)18 (11)
 Other49 (8)41 (10)8 (5)
Funding source†:
 Industry468 (80)318 (77)150 (88)
 NIH/US government64 (11)53 (13)11 (6)
 Other104 (18)84 (20)20 (12)
Trial completion date:
 Unlisted43 (7)25 (6)18 (11)
 Prior to 200511 (2)8 (2)3 (2)
 2005-0693 (16)71 (17)22 (13)
 2007192 (33)137 (33)55 (32)
 2008246 (42)173 (42)73 (43)

NIH=National Institutes of Health.

*Trials described as “phase II/III” in their registry entry are categorized as phase III.

†Trials with multiple funding sources are listed within all relevant categories; totals therefore add to more than 100%.