The present study examined various aspects of the development of learners' fluency in Japanese using a large set of speech samples collected over a long period, using an online speaking practice/assessment system called "Speak Everywhere." The purpose of the present study was to examine: (1) how the fluency related measures changed over time, and (2) which linguistic factors were correlated with each fluency measure. This study used oral production of English-speaking learners enrolled in the first year Japanese courses at a university in the U.S. The students submitted two types of speaking assignments using Speak Everywhere: (1) sentence-level oral reading and (2) short Q&A. The assignments were collected at the end of each chapter for two quarters. The study used speech rate and pause related fluency measures adapted from Ginther, Dimova, and Yang (2010). For the data analysis, we used Praat (Boersma & Weenink, 2011) for acoustic analysis and Mecab (Kudo, 2011) for morphological analysis. The results of one-way repeated measures ANOVA revealed that several measures of fluency deteriorated in both oral reading and Q&A tasks as expected from the previous research (Segalowitz & Freed, 2004). This study then examined what complexity factors affected these measures, using the mixed model approach. Overall, it was found that because various factors influence the development of fluency, temporal measures alone cannot explain fluency development. [For the complete volume, see ED574893.]