The zebrafish has been established as a mainstream research system, largely due to the immense success of genetic screens. Over 2000 mutant alleles affecting zebrafish's early development have been isolated in two large-scale morphological screens and several smaller efforts. So far, over 50 mutant strains display retinal defects and many more have been shown to affect the retinotectal projection. More recently, mutant isolation and characterization have been successfully followed by candidate and positional cloning of underlying genes. To supplement forward genetic mutational analysis, several reverse genetic techniques have also been developed. These recent advances, combined with the genome project, have established the zebrafish as one of the leading models for studies of visual system development.