The invention encompasses a method of conducting a clinical trial of a test substance from a primary site, via the internet. The internet is used in various phases of a clinical trial, including: recruiting and screening for candidates who are eligible to participate in a clinical trial of a test substance using the internet; obtaining, directly from a participant at a remote site, personal information as well as information allowing a determination of any effect(s) of the test substance on the participant after use (e.g., by evaluation forms completed and transmitted over the internet); compiling data from multiple participants.