This publication constitutes a selection of papers presented at the 6th International Symposium on the Acquisition of Second Language Speech, New Sounds 2010, held in Poznań, Poland. It consists of two volumes, presenting state-of-the-art achievements and perspectives for future research related to the acquisition of second language phonetics and phonology. The key issues include the development of explanatory frameworks of phonological SLA, the expanded scope of domains under investigation, modern methods applied in phonological research, and a new take on the causal variables related to ultimate proficiency in L2 speech. This first volume contains a selection of 27 articles that cover a wide variety of themes including L2 speech perception and production, segmental and prosodic features, as well as factors related to foreign accentedness, individual variability and ultimate achievement in the acquisition of speech.