Analysis of the human and mouse genome sequences has enabled a detailed analysis of the structure and organization of the lipoxygenase genes in the respective species. Humans appear to possess six functional genes and at least three pseudogenes while mice have seven functional genes. The arrangement of the genes is quite similar between the species with most of the human lipoxygenase genes appearing on the short arm of chromosome 17 and in mice on the syntenic portion of chromosome 11. The 5-lipoxygenase gene is unique in several respects including its distinct separate chromosomal localization and its size (4-7 x larger than other lipoxygenase genes). Three of the seven murine lipoxygenase genes have been disrupted by gene targeting. While the knockout mice appear outwardly normal, a number of important findings have been discovered using these mice and these will be covered in this review.