Objective <p>To gather all relevant literature surrounding the use of Bayesian methods in clinical trials for rheumatoid arthritis and systemic sclerosis; and to assess the use of these methods within said trials.</p> Methods <p>Medline and Embase were searched on August 18, 2024. The search strategy and screening process was performed by a single reviewer and verified by a secondary expert. We included studies that presented the primary results of a clinical trial designed to examine a treatment for either rheumatoid arthritis or systemic sclerosis, and that also included the use of a Bayesian technique. From these studies, we extracted the following information: author(s), title, year of publication, study objectives, disease under study, treatment under study, description of study sample, phase of trial, main results, description of Bayesian technique employed, and rationale for use of Bayesian technique (if applicable). The Cochrane risk of bias assessment tool was used to critically appraise each included study. Extracted data were recorded in a spreadsheet and results were synthesized narratively.</p> Results <p>A total of 11 studies were included in the final review. Seven of these studies evaluated treatments for rheumatoid arthritis, and four evaluated treatments for systemic sclerosis. A total of five Bayesian techniques were identified. These techniques included the use of posterior probabilities for efficacy analysis, simulation to estimate power and type I error for trials that employed a Bayesian analysis, Bayesian dose-finding algorithms, interim analyses using Bayesian stopping rules, and Bayesian response-adaptive randomization. A variety of rationales for the decision to use Bayesian methods were expressed.</p> Conclusions <p>The application of Bayesian methods offers many notable advantages, yet their uptake within rheumatology trials has been slow. Increased awareness of these advantages could greatly benefit the clinical trial world.</p>