We report on our preliminary experiments on building dynamic lexicons for native-speaker conversational speech and for foreign-accented conversational speech. Our goal is to build a lexicon with a set of pronunciations for each word, in which the probability distribution over pronunciation is dynamically computed. The set of pronunciations are derived from hand-written rules (for foreign accent) or clustering (for phonetically-transcribed Switchboard data). The dynamic pronunciation-probability will take into account specific characteristics of the speaker as well as factors such as language-model probability, disfluencies, sentence position, and phonetic context. This work is in a relatively preliminary stage.