["Autism Research, EarlyView. ", "\nABSTRACT\nAssessments for autism spectrum disorder are time‐consuming and expensive, and demand has increased over recent decades. Despite improved diagnostic criteria and awareness of autism, there still appear to be disparities in diagnostic rates of autism across age, gender, and ethnicity. Research investigating biases in referrals to, and assessments conducted by, autism diagnostic services is limited, especially in adults, making it difficult to understand these disparities. This clinical service evaluation collected data on demographic characteristics of clients referred and accepted for autism assessments (N = 350) and fully assessed for autism (N = 269) by a London‐based adult autism team. Demographic characteristics of clients referred to the service were compared to population prevalences using Census data to investigate potential biases in referring clinicians. Demographic characteristics of clients who received diagnoses of autism were compared to the service's average diagnostic rate to investigate potential biases in assessing clinicians. Participants referred and accepted for autism assessments were significantly more likely to be male, aged 18–34, and from White or “Other” ethnic backgrounds compared to local population prevalences. Of clients assessed, there were no significant differences in diagnostic rates of autism among demographic groups compared to the service's average diagnostic rate. Clinicians conducting autism assessments appeared to show no diagnostic bias. However, findings suggest there are still disparities in gender, ethnicity, and age of adults who were referred and accepted for autism assessments. Further research is needed to investigate causes of this access disparity to ensure people can access appropriate services and support.\n"]