The cDNAs for two casein kinase-1 homologs, hhp1 and hhp2, have been isolated from Schizosaccharomyces pombe and characterized. Their corresponding genes reside on chromosomes II and I, respectively, and encode approximately 42-46 kDa proteins that are related structurally to the HRR25 gene product of budding yeast. On the basis of multiple sequence alignment, the CK1 family appears to consist of three main branches. We predict that the branch containing the hhp genes encodes nuclear kinases involved in the regulation of DNA metabolism.