Study IDs— Use this field to search for a clinical study by an identification number.

Every clinical study is associated with identification numbers assigned to the clinical study protocol by the sponsor, funders, or others. These include unique identifiers from other registries and National Institutes of Health grant numbers. In addition, assigns a Identifier, or NCT Number, a unique identification code given to each clinical study registered on The format is the letters "NCT" followed by an 8-digit number (for example, NCT00000419).