Enhancer trap is a famous application of transposons. This method is useful for the creation of marker transgenic lines that express a reporter gene in tissue- or organ-specific manner, characterization of enhancers in the genome, finding novel patterns of gene expression, and mutagenesis. In Ciona intestinalis, efficient enhancer traps with Minos and Sleeping beauty transposons have been reported. With the enhancer trap lines, the intronic enhancers regulating the expression of the Musashi gene, the compartment in the digestive tube, the presence of enhancers sensitive to the orientation of the gene that they regulate, and the functions of the Hox1 gene have been revealed. The enhancer trap lines generated with the transposon vectors are valuable resources for use as visual markers.