ZIP1 is a novel meiosis-specific gene required for chromosome synapsis and cell cycle progression in S. cerevisiae. zip1 strains undergo homologous chromosome pairing, but are defective in synaptonemal complex (SC) formation. The zip1 mutation confers a uniform arrest in meiosis prior to the first division. zip1 strains display nearly wild-type levels of commitment to meiotic recombination; however, mature reciprocal recombinants are not formed until cells are released from meiotic arrest by return to growth medium. DNA sequence analysis of ZIP1 reveals structural homology to a number of proteins containing coiled coils. Immunofluorescence experiments using anti-ZIP1 antibodies demonstrate that the ZIP1 protein localizes to synapsed meiotic chromosomes but not to unsynapsed axial elements. Taken together, these data suggest that ZIP1 is a component of the central region of the SC. We propose a model in which ZIP1 acts as a molecular zipper to bring homologous chromosomes in close apposition.