Development of CV coarticulation was examined in one English-reared and one Japanese-reared infant. Vocalizations were collected from each child across their first two years of life. A specific CV form, common in each child's prespeech and early speech vocalizations, was selected for analysis. Coarticulation was evaluated by determining the slope of Fl and F2 transitions following consonant release. Discussion focuses on the speech motor skills characterizing coarticulation development, and the influence of English and Japanese language-learning environments.