At the following link: http://docs.moodle.org/25/en/Cohort
I find information that allows me to put many users in a cohort by uploading a single file.
Question: How do I REMOVE many users from a cohort by uploading a single file?
Quote from the Cohort link below...
Uploading users to a cohort
An administrator can upload users via CSV file to existing cohorts as follows:
Access Settings > Site administration > Users > Accounts > Upload users
Upload a text file with the following format: