Meiosis is the process which produces haploid gametes from diploid precursor cells. This reduction of chromosome number is achieved by two successive divisions. Whereas homologs segregate during meiosis I, sister chromatids segregate during meiosis II. To identify novel proteins required for proper segregation of chromosomes during meiosis, we applied a high-throughput knockout technique to delete 87 S. pombe genes whose expression is upregulated during meiosis and analyzed the mutant phenotypes. Using this approach, we identified a new protein, Dil1, which is required to prevent meiosis I homolog non-disjunction. We show that Dil1 acts in the dynein pathway to promote oscillatory nuclear movement during meiosis.