The notion that second language instruction is more effective if begun at an early age is seen as arising from cognitive-nativist and neuropsychological postulates, and from the argument of "affective purity." Each of these positions is reviewed, along with frequently-heard objections to each. A fresh perspective on the issue is thus established as a groundwork for the examination of some specific educational research that bears on the issue of optimum age. This research indicates that late instruction confers an advantage on the learner by virtue of his/her learning efficiency, while early instruction confers an advantage arising from the extended opportunities it provides for language learning in and outside school. The advantages which derive from late instruction are also conferred on the learner who begins early and continues his study through the higher grade levels. It is therefore concluded that high levels of second language proficiency are best achieved by an early start and long duration of instruction, provided that effective teaching methods are employed. (Author/JB)