Research in the acquisition of perfective and imperfective morphology has been expanding in SLA from morpheme studies to semantic, syntactic, and textual research. This volume contributes to the growing literature on the acquisition of aspect by investigating the acquisition of telicity (i.e., predicates with and without endpoints, such as Claire ate an apple vs. Clare ate apples) from a UG perspective. The hypotheses that are examined are: (a) to what extent learners transfer L1 values onto their L2, (b) whether L2 learners are capable of resetting parameters, (c) whether the acquisition of telicity co-occurs or is subsequent to the acquisition of other constructions (e.g., particles, resultatives, and double objects), and (d) whether the acquisition of these related constructions clusters with the acquisition of telicity.