Among vertebrates, the mammalian systems that are frequently used to investigate questions related to human health have gained the most benefit from microarray technology to date. However, it is clear that biological investigations and the generalized conclusions drawn from them, can only be enhanced by including organisms in which specific processes can be readily studied because of their genetic, physiological, or developmental disposition. As a result, the field of functional genomics has recently begun to embrace a number of other vertebrate species. This review summarizes the current state of microarray technology in a subset of these vertebrate organisms, including Xenopus, Rana , zebrafish, killifish (Fundulus sp.), medaka (Oryzias latipes) , Atlantic salmon, and rainbow trout. A summary of various applications of microarray technology and a brief introduction to the steps involved in carrying out a microarray experiment are also presented.