INTRODUCTION: The recent educational reform in Hong Kong calls for strengthening students' learning-to-learn ability. Portfolio learning is useful for achieving this. However, it has not been well-documented in PE. The purpose of this study was to investigate the effectiveness of portfolio learning in the affective domain. By building the portfolio, students go through the processes of goal setting, assessment for learning, and reflection, which may enhance students' learning-to-learn ability. Two research questions were: Did students and teachers favor using portfolio in PE? Were there any differences in opinions of both groups after using portfolio? METHOD: Both quantitative and qualitative methods were employed. The participants were 115 students of grades 10-12 from 4 schools and 9 teachers from 7 schools. Students set their yearly learning goals in PE, kept self and peer assessment record on physical activity checklists, and inserted self-collected learning materials in the portfolio for one year. There were pre and post questionnaire surveys for students and teachers respectively, conducted at the beginning and end of the year, to tap their opinions and changes in thinking. Focus group meetings were also conducted as a triangulation measure. RESULTS AND DISCUSSION: Both groups found portfolio useful in enhancing students' learning. For students, the means of the 6-item responses were close to or over 3 in the pre and post questionnaires using four-point Likert scale, which showed they had a positive attitude towards PE portfolio. End-of-year results indicated a significant increase in their understanding about their learning and they were more motivated to learn. For teachers, the means of the 7-item responses ranged from 2.78 to 3.67 in the pre-Q and 3.33 to 3.78 in the post-Q, which showed that they were positive towards the use of portfolio in enhancing their teaching and students' learning. Results indicated that teachers' confidence of school-based curriculum planning was significantly improved (t=2.828, p<0.05). The field notes of focus group meetings revealed that students did not favor having too much paper work and did not proactively insert learning materials in their portfolios. For teachers, they thought that portfolio helped students develop generic skills as well as values and attitudes. CONCLUSION: Simple portfolio written work was recommended to lessen the workload of students and teachers. While more investigations were beneficial in better understanding the effectiveness on the affective areas in portfolio learning, its influence on the psychomotor and cognitive areas was also worth exploring. Keyword(s): assessment, curriculum, research