The ten countries with the most number of clinical trials underway may vary over time as new trials are initiated and completed. However, as of 2021, based on available data, the ten countries with a high number of ongoing clinical trials are:
1. United States
2. China
3. Germany
4. France
5. Canada
6. United Kingdom
7. Australia
8. Spain
9. South Korea
10. Japan
Please note that this ranking can change depending on the specific time frame and the scope of clinical trials considered.