<![CDATA[The purpose of this research is to know the feasibility and the effectiveness of the assessment instrument based on performance on learning thematic students class 4 of primary school. This research method used the Research Development (R D) by Borg Gall. Population in this study were 228 of primary school students class IV in Cengkih cluster of Kalianda subdistrict South Lampung district. Samples were taken by using purposive sampling tecnique as many as 25 of primary school students in IVB grade of SD Negeri Bumi Agung and 28 of primary school students in IV grade of SD Negeri Sumur Kumbang. Data collecting technique used is non test. To collect the data, the researcher used the needs analysis, expert validation, student performance observation sheets, teacher response and student response questionnaires. The data were analyzed by using t-test formulas. This research result indicates that the instruments based this assessment performance are worth compliant substance, construction, language, as well as having proof the validity of empirical, and products instruments based this assessment performance effective it is reliable has a very high.Penelitian bertujuan untuk mengetahui kelayakan dan keefektivan instrumen penilaian berbasis kinerja pada pembelajaran tematik SD. Metode penelitian yang digunakan adalah penelitian dan pengembangan oleh Borg Gall. Populasi pada penelitian ini siswa kelas IV sebanyak 228 orang di Gugus Cengkih Kecamatan Kalianda Kabupaten Lampung Selatan. Sampel diambil dengan menggunakan teknik purposive sampling sebanyak 25 siswa kelas IVB SD Negeri Bumi Agung dan 32 siswa kelas IV SD Negeri Sumur Kumbang. Teknik pengumpulan data yang digunakan adalah non tes yang terdiri dari; angket analisis kebutuhan, angket validasi ahli, lembar pengamatan kinerja siswa, dan angket respon guru. Data dianalisis menggunakan rumus Uji t. Hasil penelitian menunjukkan bahwa produk instrumen penilaian berbasis kinerja dikategorikan layak memenuhi persyaratan substansi, konstruksi, bahasa, serta memiliki bukti validitas empirik, dan memiliki tingkat reliabilitas yang sangat tinggi.Kata kunci: instrumen, pembelajaran tematik, SD]]>
