The importance of the prosodic features of the phonological component of language in converting underlying grammatical structure into patterns of sound is discussed. Examples are given of data equating prosodic features of English pronunciation with required lexico-syntactic changes in Spanish in order to delineate possible areas of first language interference for Spanish speakers learning English as a second language. It is shown that what is stated at the levels of lexicon or syntax in Spanish can often be expressed only at the phonological level in English. Language instructors should be aware of sounds in one language which are totally lacking in the sound system of another, sounds which are phonemically distinct in one language but mere phonetic variants in another, and sounds which occur in both languages but whose pattern of occurrence is different in each language. The teaching of pronunciation must be a continuous activity in which substantial attention is paid to the prosodics of phonology. (RW)