Fossilization is a noticeable characteristic of second language acquisition. Some researchers claim that while it is possible for child learners to acquire native-like competence in the L2, adult learners can never succeed regardless of continuous exposure to input, adequate ability and motivation to learn, and sufficient opportunity to practice. A number of causal variables have been identified to account for incomplete L2 ultimate attainment, among which lack of instruction is considered to be one of the major factors. This study investigates the extent to which focused instruction can affect learners9 output, especially that of a fossilized deviant form. Participants are 29 Japanese EFL learners. Comparison of substitutions of [r] for the English /r/ before and after instruction shows improved performance in 76% of the participants. In addition, the participants pronounce /r/ in words beginning with wr far more accurately than those with an r. These findings suggest that learners can be trained to improve their production of a difficult sound and that it is possible for persistent errors to destabilize and gradually move toward the target forms.