BACKGROUND: Amongst other things, the drug regulator, Central Drugs Standard Control Organization (CDSCO), is responsible for regulating clinical trials that underlie drug approvals in India. Since 2009, CDSCO has mandated that all regulatory clinical trials be registered with the Clinical Trials Registry - India (CTRI). In this study, we aimed to determine whether regulatory trials, for which CDSCO had given permission, were registered with CTRI as required. We also aimed to quantify missing CTRI records, if any. METHODS: This study involved regulatory trials, for which CDSCO permission letters were available. The permission letters, available as portable document format (PDF) files, were analysed to extract trial titles and protocol numbers. These data were then used to search the CTRI database, which was initially downloaded on 19 January 2024 and updated in August 2024, for matching records. The matches were confirmed by cross-referencing titles and protocol numbers, ignoring protocol version variations. RESULTS: Of the 381 trials examined, 335 (88%) had corresponding CTRI records, whereas 46 (12%) did not. CONCLUSIONS: This study highlights that not all regulatory trials approved by CDSCO are registered with CTRI, despite legal requirements. The absence of a significant number of trials from CTRI raises concerns about transparency in the clinical trial enterprise in India. To improve trust and regulatory compliance, it is essential to establish explicit linkages between CDSCO and CTRI records to avoid the challenges of identifying matches. This study contributes to ongoing efforts to increase transparency and accountability in clinical trial registration in India.