Monitoring constitutes the primary mechanism by which sponsors maintain oversight of clinical trials and fulfill their regulatory obligation to ensure proper trial conduct. Through systematic evaluation of trial activities and documentation, monitoring aims to protect the rights and well-being of trial subjects, verify that reported data are accurate, complete, and verifiable against source documents, and confirm that the trial is conducted in compliance with the protocol, GCP, and applicable regulations.

Monitoring activities encompass both on-site and centralized approaches. On-site monitoring involves physical visits to investigational sites, where monitors review source documents, verify data accuracy, assess regulatory compliance, and evaluate site processes. Centralized monitoring involves remote review of accumulating data to identify patterns, trends, and inconsistencies that may indicate problems with data quality, site performance, or protocol compliance. Modern monitoring strategies typically combine both approaches, leveraging the complementary strengths of each.

The extent and nature of monitoring should be determined by the sponsor based on a risk assessment that considers factors such as the trial's objectives, complexity, and endpoints; the volume and complexity of data collected; the risks to participants; and the performance history of investigational sites. This risk-based approach, emphasized in ICH E6(R3), allocates monitoring resources to activities most likely to protect participants and ensure data quality, rather than applying uniform monitoring intensity regardless of risk.