The central purpose of this study is to illustrate how ESL instructors can take a principled approach to setting pronunciation instruction priorities for learners. Elicited speech samples from 30 adult English learners were analysed for suprasegmental and segmental pronunciation features. Guided by Levis’ (2005) intelligibility principle, results of the analysis led to recommended foci for pronunciation instruction. The study’s participants come from three distinct first language (L1) backgrounds (Mandarin Chinese, Colombian Spanish, and Slavic), reflecting the type of linguistic breadth found in typical ESL classrooms. It is recommended that problematic features observed in the speech of participants from all three L1s be addressed as a whole group, with each L1 group also receiving separate instruction for their specific difficulties. Finally, results of the speech analysis are compared with previously published material describing L1-specific pronunciation difficulties.