The product of the maternally acting gene zyg-11 is required for early embryogenesis of Caenorhabditis elegans. One-cell embryos that lack a functional zyg-11 gene product exhibit an arrest of meiosis at metaphase II, a delay in the formation of pronuclei, unusually vigorous movements of cytoplasm, the formation of multiple pronuclei, incorrect segregation of P granules, and incorrect placement of the first cleavage furrow. We have isolated and sequenced a molecular clone of zyg-11, and shown that microinjection of the cloned DNA can rescue zyg-11 mutations. A transcriptional analysis shows that transcription of the gene is not limited to the female germ-line, despite the strict maternal-effect phenotype of zyg-11 mutations.