Recent empirical research in sociolinguistics and social psychology has established the existence of the socio-psychological phenomena known as linguistic stereotyping (LS) and reverse linguistic stereotyping (RLS), which have an implicit or unconscious effect on listeners' perception of speech and speakers. Despite such findings, little research has explored the role these phenomena may play in the rating of speaking proficiency as assessed by Oral Proficiency Interview (OPI) testers. This article provides an overview of the OPI instrument followed by a review of some published criticisms thereof. These criticisms are expanded upon through a review of research on LS, RLS, standard language ideology, the native speaker construct, and the co-construction of speaking performance with particular emphasis on research concerning Spanish dialect perception. The article concludes with a discussion of the implications of this research for the assessment of speaking proficiency, and a call for further research in several areas in order to better understand and mitigate the potential for these phenomena to cause bias in the high stakes assessment of speaking proficiency.