ABSTRACT: Protein kinase CK1 is a ser/thr protein kinase family which has been identified in the cytosol cell fraction, associated with membranes as well as in the nucleus. Several isoforms of this gene family have been described in various organisms: CK1, CK1, CK1, CK1 and CK1. Over the last decade, several members of this family have been involved in development processes related to wnt and sonic hedgehog signalling pathways. However, there is no detailed temporal information on the CK1 family in embryonic stages, even though orthologous genes have been described in several different vertebrate species. In this study, we describe for the first time the cloning and detailed expression pattern of five CK1 zebrafish genes. Sequence analysis revealed that zebrafish CK1 proteins are highly homologous to other vertebrate orthologues. Zebrafish CK1 genes are expressed throughout development in common and different territories. All the genes studied in development show maternal and zygotic expression with the exception of CK1. This last gene presents only a zygotic component of expression. In early stages of development CK1 genes are ubiquitously expressed with the exception of CK1. In later stages the five CK1 genes are expressed in the brain but not in the same way. This observation probably implicates the CK1 family genes in different and also in redundant functions. This is the first time that a detailed comparison of the expression of CK1 family genes is directly assessed in a vertebrate system throughout development.