This thesis investigates the processes learners go through in learning the pronunciation of a second language, and how teachers can facilitate these processes. Its focus on the cognitive has led to the development of general teaching principles and the development of theory. It brings theory and practice together by using practice to inform theory and theory to re-inform practice. A broad multi-disciplinary approach has been taken, drawing on insights from phonology and L2 speech research, pronunciation pedagogy, and theoretical insights from SLA (Second Language Acquisition), socio-cultural theory and educational psychology, and bringing these together under a unifying theory of Cognitive Phonology. The empirical evidence to support both the theoretical and practical conclusions reached is provided through a progressive series of qualitative and quantitative studies. These studies all focus on difficulties in pronouncing syllable codas, i.e. epenthesis (the addition of a vowel) and absence (inappropriate omission of a consonant), in the context of adult high-intermediate level ESOL students resident in New Zealand. ... This thesis finds there is a role for form-focused instruction and corrective feedback in pronunciation learning. While this is in line with many views within SLA theory, it is only by turning to Cognitive Phonology that the necessary distinctions can be drawn between types of instruction in order to reveal what it is that makes explicit instruction effective. These theoretical insights are shown to have practical applications for the classroom.