Table 1

Characteristics of studies registered on the website1

Study characteristicNumber%
Total studies registered in the USA54890100
Sex of study subjects
 Females only53149.7
 Males only21704.0
 Both sexes combined4735586.3
 Not indicated51<0.1
Age of study subjects
 Adults (including seniors)4228377.0
 Both adults and children964617.6
 Not indicated9<0.1
Study phase
 Phase I814514.8
 Phase II1591129.0
 Phase III814214.8
 Phase IV42927.8
 Phase not indicated1840033.5
Source of funding
 Blended (industry plus non-industry)647711.8
 Source of funding not indicated11<0.1
  • 1CTG began accepting trial registrations on 1 November 1999.

  • *The breakdown of non-industry-sponsored studies is as follows:

    • 6480 trials for which NIH was the sole sponsor;

    • 1227 trials sponsored by another US Federal agency;

    • 10 166 trials with multiple non-industry sources of funding (including NIH); and

    • 14 626 trials for which the funding source was listed as ‘other’ or was not listed.