This mutual intelligibility study contains two experiments: the production and the perception of English monophthongs. In the production experiment, 45 male and 45 female first-year Chinese college students were recorded. They hailed from nine different dialectal backgrounds (three supergroups), with five male and five female speakers per dialect group. The stimuli were [hid], [hɪd], [hed], [hæd], [huːd], [hʊd], [hɔːd], and [hɔd].Formants F1 and F2 as well as vowel durations were measured. Linear Discriminant Analyses showed that the speakers’ dialect backgrounds can be predicted better than chance only on the supergroup level. In the perception part, one representative male speaker was chosen for each dialect based on his Euclidian distance from a model American speaker. The representatives’ vowel tokens were then identified and rated for typicality by two 282 first-year undergraduates from the same dialect groups. A significant interlanguage benefit (i.e. better identification results when listener and speaker share the same language background) was found only on the dialect supergroup level.