We have characterised the zebrafish ortholog, setb, and investigated its role in embryogenesis. Phylogenetic analysis showed that zebrafish Setb has an amino acid sequence identity of approximately 96% with the mammalian orthologs. Whole mount immunofluorescence analysis revealed that Setb is expressed mainly in the eye, the lateral line neuromasts and the olfactory pit. Knockdown of setb using antisense morpholino oligonucleotides resulted in increased apoptosis, reduced cell proliferation and severe morphological defects. The morphant phenotypes were partially rescued when setb MO1 was co-injected with human set mRNA. In vivo labelling of hair cells in the lateral line of setb morphants with the vital fluorescent dye FM1-43 showed a significant decreased number of functional neuromasts. Gene expression analysis of setb morphants, employing DNA microarrays revealed a role of Setb in neurogenesis and the mechanosensory lateral line system.