Clinical trials are governed by principles of good clinical practice (GCP), which can strengthen the achievement of rigor, reproducibility, and transparency in scientific research. Rigor, reproducibility, and transparency are key for producing findings with greater certainty. Clinical trials are closely supervised, often by a clinical trial coordinating center, data safety and monitoring board, and a funding agency, with policies that are a manifestation of GCP and support rigor, reproducibility, and transparency. The multisite Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study is an example clinical trial of relevance to a psychology and aging audience that utilized many protocols that can be applied to single-laboratory designs, including a manualized protocol with accompanying scientific rationale, predefined analysis plans, standardization of procedures across field sites, assurance of competence of study staff in study procedures, transparent coding/entry/transmittal of data, regular quality assurance, and open publication of data. Despite substantial resource discrepancies between the two, single-laboratory studies can model the GCP principles utilized in large clinical trials to provide an excellent foundation for rigor, reproducibility, and transparency. (PsycInfo Database Record (c) 2022 APA, all rights reserved).