In a very large number of studies, James E. Flege and his colleagues have examined the influence of different subject variables on immigrants’ success in learning an L2. In this paper , possible implications of Flege’s research for the foreign language classroom are discussed. The results obtained by Flege in studies examining the acquisition of L2 speech sounds and L2 morphosyntax suggest that four factors should particularly help students in a foreign language classroom to develop a high level of second language proficiency. These four factors are a) an early starting age, b) intensive use of the foreign language over a period of many years, c) exposure to a substantial amount of high-quality input, and d) training in the perception and production of L2 sounds.