The metallothionein-human growth hormone fusion gene (MThGH), constructed by fusing the mouse metallothionein promoter with the human growth hormone gene, was microinjected into the cytoplasm of one-cell embryos of channel catfish Ictalurus punctatus. The 3-week-old fish that developed were analyzed for integrated copies of the MThGH gene. Two of 10 animals contained MThGH sequences that comigrated with genomic DNA of high molecular weight in southern blots. The MThGH sequences were organized in head-to-tail tandem arrays that are characteristic of foreign genes integrated into recipient cell genomes. These data strongly suggest that the MThGH genes are stably integrated into chromosomal DNA, and that transgenic channel catfish can be generated by cytoplasmic injection of early embryos.