This study aimed at exploring motivational factors among American college and university students studying Japanese (as a second/foreign) language by examining their Peak Learning Experiences (Anderson et al., 2001; Bloom, 1982). In all, 128 students studying intermediate Japanese at five different schools returned their answers to this study's survey questionnaire. They were asked to write about (1) the most helpful/encouraging experience that had assisted them in learning Japanese and (2) the most difficult/discouraging experience that had prevented them from learning it well. The most frequently mentioned "positive" Peak Learning Experiences (PLEs) were (1) being understood by native speakers of Japanese (58%), (2) the enthusiasm and patience of the teachers (13%), (3) classroom immersion in authentic Japanese materials (12%) and (4) use of authentic materials in the classroom (8%). The most common "negative" Peak Learning Experiences (NLEs) for students were when they failed to see any progress in their learning (22%). The implications of the study for Japanese language teaching and curriculum design are discussed.