Genetic and molecular analyses of Drosophila development mutants led to the discovery of homeotic genes which control segmental identity in the fruit fly. All of the known homeotic genes contain a conserved protein-encoding DNA sequence of about 180 bp, named the homeobox, which is present in multiple copies in the genomes of most higher animal species. By using a Drosophila homeobox-containing gene from the Antennapedia (Antp) complex as a probe, Southern hybridization revealed that there are at least two homeobox-containing genes in carp. RNA slot hybridization showed that the Antp-like gene(s) expresses intensively in the carp intestine, eye, kidney, and heart, less intensively in the liver, testis, and cerebellum, but not at all in the cerebrum, pituitary gland, and muscle. Northern hybridization revealed that there are at least five transcripts present in the carp embryo and each expresses in a unique, stage-dependent pattern.