This paper presents a selective overview of studies that have examined age effects in second language (L2) acquisition. The focus was on adult second language learners and the L2 ultimate attainment at syntax-interface morphology, with particular attention given to the problematic case of inflectional morphology. We present different kinds of evidence including behavioural, descriptive and brain-based data. Although the main focus was on the syntax-morphology interface, other domains such as semantics, phonology were also briefly mentioned. Learners involved come from different L1 backgrounds. The results show that there is a general divergence between native and non-native speakers, however certain exceptions are noted. The paper is an addition to the existing body of literature in the field of second language acquisition on critical periods, age effects in language acquisition, and endstate grammars.