AbstractTujuan penelitian ini adalah untuk mengetahui keefektifan pembelajaran Snowball Throwing berbantuan LKS terhadap hasil belajar siswa kelas VIII SMP Negeri 1 Kaliori pada materi lingkaran tahun ajaran 2011/2012. Populasi dalam penelitian ini adalah semua siswa kelas VIII SMP Negeri 1 Kaliori tahun ajaran 2011/2012. Sampel dalam penelitian ini diambil secara cluster random sampling. Data hasil penelitian diperoleh dengan metode tes yang dianalisis dengan menggunakan uji proporsi, uji rata-rata, uji kesamaan dua proporsi, dan uji perbedaan dua rata-rata untuk menguji hipotesis. Hasil penelitian menunjukkan: (1) zhitung )=0,5>-(z(0,5-α) ) )=-1,64, artinya siswa yang tuntas terhadap hasil belajar pada kelas eksperimen dapat mencapai persentase ketuntasan minimal siswa, (2) thitung=3,9001 >t(1-α) =1,69 artinya rata-rata hasil belajar siswa pada kelas eksperimen dapat mencapai KKM, (3) zhitung=2,335>z(0.5-α) )=1,64, artinya siswa yang tuntas pada kelas eksperimen lebih besar dari kelas kontrol, (4) thitung=2,0194 ≥ 1,668, artinya rata-rata hasil belajar siswa pada kelas eksperimen lebih dari kelas kontrol. Berdasarkan hasil penelitian tersebut dapat disimpulkan bahwa penerapan Pembelajaran Snowball Throwing berbantuan LKS efektif terhadap hasil belajar siswa kelas VIII SMP Negeri 1 Kaliori pada materi lingkaran.The purpose of this study was to determine the effectiveness of Snowball Throwing learning assisted students’ worksheets to learning outcomes of VIII grade in SMP Negeri 1 Kaliori in circle material of the school year 2011/2012. The population in this study were all students in VIII grade SMP Negeri 1 Kaliori academic year 2011/2012. The sample in this study were drawn by cluster random sampling. Research data obtained with the test method were analyzed using the proportion test, test averages, test the equality of two proportions, and test the average difference in the two hypotheses. The results showed: (1) zcount = 0.5> - z(0,5-α) = -1.64, meaning that students who complete the results of experiments studying the class could achieve a minimum percentage of completeness students, (2) tcount = 3.9001> t(1-α) = 1.69 means that the average student learning outcomes can be achieved in the experimental class KKM, (3) zcount = 2.335> z(0.5-α ) = 1.64, meaning that students who completed the experimental class is greater than the control class, (4) tcount = 2.0194 ≥ 1.668, meaning that the average student learning outcomes in the experimental class over the control class. Based on these results we can conclude that the application of Snowball Throwing learning assisted Student’s Worksheet effective against student learning outcomes VIII grade SMP Negeri 1 Kaliori in circle material.