The purpose of this study is to investigate the durability of the effect of explicit and implicit instructions on beginning EFL learners' learning of the copula "be". The study intends to examine whether or not the effect remains after the auxiliary "be" of the progressive is introduced. Three groups of 89 Japanese junior high school students participated in the quasi-experiment. One group was given explicit instruction on the rule of the copula "be". Another group was given implicit instruction under which the participants memorized exemplars without focusing on the rule. The third group was not given any treatment on the target structure. After progress was measured with a pretest and two post-tests, the three groups were provided with the same form-focused instructions on the progressive. Then, three further post-tests were given to see if the instruction on the auxiliary "be" had any impact on the mastery of the copula "be". Major findings were (1) explicit instruction had positive effects in the short term, while implicit instruction did not; (2) the effects of the former did not last, especially after presentation of the progressive. The findings indicate that instruction after explicit instruction must include some adjustments to retain its effect. (Contains 7 tables and 6 figures.)