Purpose of the study: The purpose of the study is to describe the results of the development of authentic problem-based assessment models in learning Indonesian in high school. This development uses the Plomp model which has stages, preliminary research, prototyping, and evaluation. The product developed is a problem-based authentic assessment model book and a teacher's manual. Both books were tested for validity, practicality, and effectiveness well.
 Methodology: The development of this research follows the preliminary, prototype and evaluation research stages. The three steps are carried out selectively. The validity of the model is obtained from an expert judgment of the problem based authentic assessment model book and the problem based authentic assessment handbook. The trial was conducted in class XI of high school to see the practicality and effectiveness of the model book and the guidebook.
 Main Findings: The development of this authentic problem-based assessment model has produced model books and manuals for Indonesian language teachers in high schools. The results of this study indicate that (1) the problem-based authentic assessment model is very valid, (2) the problem-based authentic assessment model is very practical, and (3) the problem-based authentic assessment model is very effective in learning Indonesian.
 Applications of this study: Teachers can more easily assess the process and learning outcomes in learning Indonesian. The problem-based authentic assessment model can be used in language skills (listening, speaking, reading and writing). The teacher can develop appropriate assessment instruments used to assess students' knowledge, attitudes, and psychomotor. The grades obtained are not only numerical but in the form of student work.
 Novelty/Originality of this study: This authentic problem-based assessment model presents problems in the form of text or questions to be answered by students. Assessment instruments are presented to teachers to assess students' attitudes, cognitive, and psychomotor. The teacher can judge according to the student's ability to answer the questions given. Furthermore, to assess student and psychomotor attitudes, teachers can use portfolio and project instruments.