This study investigated factors that could affect inter-examiner reliability in the pronunciation assessment component of speaking tests. We hypothesized that the rating of pronunciation is susceptible to variation in assessment due to the amount of exposure examiners have to nonnative English accents. An inter-rater variability analysis was conducted on the English pronunciation ratings of three test candidate interlanguages: Chinese, Korean, and Indian English. Pronunciation was rated by 99 International English Language Testing System (IELTS) examiners across five geographically dispersed test centres. The examiners had either prolonged exposure, or no, or little exposure to the interlanguage of the candidates. A significant proportion of examiners rated pronunciation higher when they had prolonged exposure, and lower when they had no, or little, exposure to the candidates' interlanguage. The location of the test centre also had a significant effect on the pronunciation rating, independent of the familiarity variable, with a significant proportion of NNS raters scoring candidates from their home country higher than those who were not. It is recommended that interlanguage phonology familiarity should be considered in the design of speaking tests and rater training and that research is required into test centre bias and the phonological judgements and awareness of OPI raters.