Evidence-based standards in proficiency are needed for ultrasound-guided peripheral intravenous access. In this study, we explored the validity of the Peripheral Ultrasound-Guided Vascular Access (P-UGVA) Rating Scale. We recruited 3 groups of physicians (5 novices, 5 intermediates, and 5 experts) of increasing proficiency in peripheral ultrasound-guided intravenous access. All participants performed 3 peripheral ultrasound-guided intravenous accesses on three different patients. Performance was video-recorded by 3 cameras and the ultrasound image. Synchronized and anonymized split-screen film clips were rated using the P-UGVA rating scale by 2 assessors, which also assessed overall performance on a 1-5 Likert-scale. Evidence of validity was explored using the contemporary validity framework by Messick (content, response process, internal structure, relations to other variables, and consequences). Content and response process was ensured in the development of the rating scale and validity study. Internal consistency of the P-UGVA rating scale was excellent and sufficient high for certification purposes (Cronbach's alpha = 0.91). Proficiency groups were successfully discriminated by the UPGIVA rating scale (P =.029, one-way ANOVA), and the P-UGVA rating scale scores also correlated strongly with the overall performance evaluations (rho=0.87, P<.001, Pearson correlation). We calculated a pass/fail score of 29, which lead to a theoretical false positive rate of 26.5% and false negative rate of 8.5%. We present validity evidence for the P-UGVA rating scale and an evidence-based standard in proficiency for ultrasound-guided peripheral intravenous access.