The present study investigates the relative effects of processing instruction (PI) and meaning-based output instruction (MOI) on the acquisition of Japanese honorific expressions. The PI and MOI treatments were designed to be identical except for the practice mode (input vs. output) and treatments were provided via computer-based materials. Eighty-five intermediate-low Japanese learners were randomly assigned to PI (n = 29), MOI (n = 28), and Control (n = 28). Learners performance on the target grammar points were measured by four comprehension tasks (the word recognition task, the word fill-in-the-short-conversation task, the sentence comprehension task, and the reading comprehension task) and four production tasks (the word production task, the fill-in-the-short-conversation task, the sentence production task, and the word-revision-in-a-discourse task), using a pretest and two posttest design. The results showed the superior effect of MOI over PI on the word production and the fill-in-the-short-conversation, the sentence production, and the word-revision-in-a-discourse task for the regular verbs. The relative effect of PI and MOI were found on all the recognition and production tasks for the irregular verbs and the word-revision-in-a-discourse task for the regular verbs. The positive effect of PI on the acquisition of the irregular verbs, limited effect of PI on the production tasks and the effect of MOI on the reading comprehension are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]