ABSTRAKTujuan penelitian ini adalah untuk meningkatkan hasil belajar matematikamateri bangun ruang melalui model Problem Based Learning pada siswa kelas V SDNegeri 3 Kiringan Tahun Ajaran 2011/2012.Bentuk penelitian ini adalah penelitian tindakan kelas, yang terdiri dari duasiklus. Tiap siklus terdiri dari empat tahap yaitu perencanaan, pelaksanaan,observasi, dan refleksi. Teknik pengumpulan data menggunakan metode observasi,tes, dokumentasi, dan wawancara. Validitas data menggunakan teknik triangulasisumber, metode, penyidik, dan teori serta validitas isi. Indikator kinerja yangditetapkan yaitu pada akhir siklus siswa mencapai KKM (nilai 70) sebesar 80% darijumlah siswa kelas V. Teknis analisis data menggunakan analisis deskriptifkomparatis dan kritis.Hasil penelitian diperoleh kesimpulan model Problem Based Learning (PBL)dapat meningkatkan hasil belajar matematika pada siswa kelas V SD Negeri 3Kiringan Kecamatan Boyolali Kabupaten Boyolali Tahun 2011/2012. Hal iniditunjukkan dengan hasil belajar siswa pada kondisi awal, nilai tertinggi 78 danterendah 50, siswa mencapai KKM sebanyak 6 siswa (31,58%) dengan rerata sebesar63,11. Pada siklus I hasil belajar siswa yaitu nilai tertinggi 80 dan terendah 60, siswamencapai KKM sebanyak 14 siswa (72,68%) dengan rerata 70,42. Pada siklus IIhasil belajar siswa yaitu nilai tertinggi 85 dan nilai terendah 70, siswa yang mencapaiKKM sebanyak 19 siswa (100%) dengan rerata 76,32.Kata Kunci: Hasil Belajar Matematika, Model Problem Based LearningABSTRACTThe objective of this research is to improve the learning result inMathematics on the topic of discussion of Geometry through the Problem-BasedLearning of the Students in Grade V of State Primary School 3 of Kiringan inAcademic Year 2011/2012.This research used the class action research (CAR) method with two cycles.Each cycle consisted of four steps, namely: planning, implementation, observation,and reflection. The data of research were collected through observation, test, and indepthinterview. They were validated by using the data source triangulation, methodtriangulation, theory, and content validity, investigator, theory, and content validity.The performance indicator set in final cycle was at least 80% of students couldaccomplish the minimum learning completeness criterion score i.e. 70. The data ofresearch were analyzed by using the descriptive comparative and critical analysis.The result of the research shows that Problem Based Learning (PBL) canimprove the learning result in Mathematics on the topic of discussion of Geometrythe students in Grade V of State Primary School 3 Kiringan in Academic Year2011/2012. Prior to the treatment, the highest score was 78 and the lower score was50, and the number of students who fulfilled the minimum learning completenessscore criterion was (6) 31.68% with the average score of 63.11. Following thetreatment, the highest score became 80 and the lower score became 60, and thenumber of the students who fulfilled the minimum learning completeness scorecriterion was 14 (72.68%) with the average score of 70.42 in Cycle I. In addition, thehighest score became 90 and the lower score became 70, and the number of thestudents who fulfilled the minimum learning completeness score criterion was 19students (100%) with the average score of 76.32 in Cycle II.Keywords: Learning result in Mathematics, problem-based learning