Although Computer-Assisted Language Learning (CALL) provides EFL (English as a Foreign Language) students a dynamic environment for English learning, many courses in current markets still emphasize the presentation of domain knowledge but neglect how the students truly interact with the lessons. This article describes the development of Hypermedia-based English Learning system for Prepositions (HELP), which provides EFL students learning diagnosis and remedial instruction according to student confidence scores (CR). Details include how the system diagnoses students' error types in English prepositions and provides adaptive remedial instructions. This study also investigated the effects of two design factors: (1) student confidence ratings (CR) for answers, and (2) the provision of adaptive remedial instruction on EFL students' English prepositions learning in adaptive hypermedia. A pretest?posttest control-group experiment involving 88 EFL students was employed. Results of this study revealed significant effects of student confidence ratings (CR) and the provision of adaptive remedial instruction for English prepositions learning in hypermedia-based lessons.