Background <p>Accrual of participants into clinical trials is a fundamental and important aspect for the management of trial progress. Monitoring of trial accrual often provides insight into the potential timing of key study events, such as interim analysis, as well as the feasibility of the overall trial to enroll the projected sample size in the original estimated timeline.</p> Methods <p>A Bayesian first order simple dynamic linear model with weakly informative priors is utilized to characterize enrollment rates temporally within pre-defined time windows (quarterly) for the duration of a trial.</p> Results <p>Application of the model to three ongoing clinical trials demonstrates the utility of the model to characterize the observed accrual patterns. Additionally, the applications demonstrate the flexibility of the model to react to variable accrual patterns without overreacting to the variability of accrual within a trial due to expected causes, such as seasonal variability in disease incidence, or unexpected causes, such as a global pandemic.</p> Conclusions <p>Much statistical literature has been dedicated to predicting when key study events are likely to occur by utilizing current estimated rates of participant accrual; however, study teams, sponsors, and funding agencies have interest in the previous trends in participant accrual. This work presents an addition to the literature which allows parties interested in assessing trial progress to do so by providing a flexible framework for the standardized characterization of trial accrual which is not overly sensitive to the expected variability of trial accrual.</p>