This study made an attempt to verify the claim that Japanese EFL learners do not always acquire English grammatical features immediately after classroom instruction. The researcher examined the time gap between instruction and acquisition of five grammatical items (the present tense, to-infinitive, passive construction, relative clause, and the subjunctive mood). The result we obtained from two kinds of tasks (free composition task and translation task) showed that students needed at least more than one year to acquire a certain grammatical feature and the time length from instruction to acquisition is different from item to item. We also obtained a few interesting results by analyzing our subjects' errors in the translation task. One is that learners were sometimes influenced by Japanese expressions to choose which item to use. Another finding is that they were confused in choosing an item by other grammatical items that belonged to the same grammatical category such as tense and aspects. These findings challenge the way in which of evaluation is usually made by Japanese teachers of English; that is, while Japanese learners of English need a certain period of time to acquire a grammatical item, teachers tend to test their abilities of that particular item and expect to acquire it soon after the instruction.
