The present study evaluates the relative effectiveness of two types of input-based instruction, structured input instruction (a structured input task only) and structured input instruction with feedback (the structured input task + reactive explicit feedback) for teaching English polite requestive forms, involving 45 Japanese learners of English. Treatment group performance was compared to that of a control group on the pre-tests, post-tests, and follow-up tests: a discourse completion test, a role-play test, a listening judgement test, and an acceptability judgement test. The results of data analysis indicate that the two treatment groups performed better than the control group, and that the explicit reactive feedback was not always indispensable in the structured input task. (Contains 2 tables and 4 figures.)