In this article, I present a longitudinal study of a child's (male, aged 3;0-3;4) acquisition of intervocalic consonants characterized within the framework of Optimality Theory (OT). At Stage I, the child presents with unusual error patterns, weakening and labial substitution, and shows evidence of phonologically opaque surface forms. These patterns persist at Stage II despite elaboration of phonemic contrasts intervocalically. In addition, a new error pattern emerges, nasal harmony, along with additional opaque forms. Although the errors exhibited by the child are somewhat atypical of those generally observed in acquisition, they are, nevertheless, entirely consistent with cross-linguistic facts. Further, although phonological opacity is a linguistic phenomenon that poses a challenge to nonderivational theoretical frameworks such as OT, I offer McCarthy's (2002; 2003a) comparative markedness approach as a solution to this problem that is theoretically superior to alternatives.