The research addresses three research objectives: (1) to identify learning strategies of writing skill used by senior high school students in Indonesia, (2) to measure the extent of use of the strategy categories, and (3) to study the differences in the use of the strategies by successful and less successful learners. The subjects of the study were 766 second year senior high school students in East Java, Indonesia. They were asked to complete a questionnaire of strategies of learning writing skill and a self-assessment. The results of the data analysis using Principal Component Analysis yielded twelve components with an initial eigenvalue greater than 1, explaining a cumulative variance of strategies 57.68%. The component matrix was rotated using Varimax with Keiser Normalisation Method and the resulting factors were then treated as posteriori strategy categories and named self-monitoring, language-focusing, planning, metacognitive affective, cognitive compensation, self-evaluating, social process-focusing, authentic practicing, meaning-focusing, vocabulary developing, metacognitive commencement, and mental processing strategies. All of these strategies were used at the moderate frequency level. Finally, successful learners reported using the strategies more frequently than less successful learners did.