Discussion of the roles of input and output has been attracting a number of researchers in second language acquisition (e.g., DeKeyser, 2007; Doughty, 1991; Krashen, 1982; Long, 1983; Norris & Ortega, 2000; Swain, 2000), and VanPatten (2004) advocated that both structured input and structured output allow learners to process input properly. Some researchers explored the comparative effectiveness of traditional instruction and structured input (e.g., Benati, 2004), and others observed the effectiveness of structured input and structured output on receptive and productive knowledge (e.g., Keating & Farley, 2008). The present study investigated structured input and structured output in the acquisition of Japanese. Two experimental groups (N = 15 and N = 12) received either structured input or structured output activities during class on two successive days. Analyses of pretest, immediate posttest, and delayed posttest data showed that both types of activity were equally effective in improving learners' receptive and productive knowledge.