This study contributes to the literature on second language (L2) learners' revision behavior by describing what, when, and how often L2 learners revise their texts when responding to timed writing tasks on the computer and by examining the effects of task type, L2 proficiency, and keyboarding skills on what and when L2 learners revise. Each of 54 participants with 2 levels of L2 proficiency (low vs. high) and 2 levels of keyboarding skills (low vs. high) responded to timed independent and integrated writing tasks on the computer. A keystroke logging program recorded each participant's writing activities. Keystroke data were coded in terms of participants' revision behavior (e.g., orientation, linguistic domain, and temporal location of revisions) and then compared across tasks and learner groups. The findings suggest that the participants tended to revise form more often than content and that L2 proficiency and, to a lesser extent, task type, but not keyboarding skills, affected participants' revision behaviors during the timed writing tasks. Overall, the participants made more precontextual (that is, at the point of inscription) revisions than contextual revisions (that is, revisions of already written text), made considerably more typography and language revisions than content revisions, revised more frequently at the phrase and word level than at higher levels, and tended to make precontextual revisions more frequently in the first two thirds of the writing process and contextual revisions most frequently in the last third of the writing session. The findings and their implications for practice and research are discussed.