In second language acquisition (L2A) research, ultimate attainment refers to the outcome or end point of acquisition, and is used interchangeably with the terms final state, end state, and asymptote."Ultimate" is not to be thought of as synonymous with "nativelike," although nativelikeness is one of the observed outcomes of L2A.Most L2A studies have focused on the initial state, stages in L2 development, and rates of acquisition. However, data from such studies do not directly speak to the potential of the learner, which is an inescapable consideration of L2A theory. As we will see, the study of ultimate attainment engages such core L2A issues as native-language influence, access to Universal Grammar, maturational effects, and fossilization.