This document summarizes research on factors affecting late second language acquisition. It discusses how age of acquisition can influence adult learners' ultimate attainment of pronunciation and other language skills. Specifically, it summarizes a study that found age of arrival predicted pronunciation abilities in spontaneous but not controlled speech. Exposure to an L2 environment alone does not ensure language development, as amount and type of use depends on individual choices and circumstances. While age and aptitude impact late L2 acquisition, motivational and social factors must also be considered. Teachers must help learners of various ages and abilities given input limitations in EFL contexts by addressing cognitive, motivational, and sociocultural factors.