Transgenic mouse lines were generated using either 3.8 or 1.1 kb of 5' upstream flanking sequence from the human blue opsin gene fused to the lacZ or human growth hormone reporter gene. Mice were analyzed for appropriate cell-specific and developmental expression patterns. In 13 independently derived lines of animals, transgene expression was limited to photoreceptor and inner nuclear layer cells. Photoreceptors were identified as cone cells based on morphological criteria and colocalization of transgene expression with the cone-associated marker, peanut agglutinin lectin. More specifically, transgene-positive photoreceptors were identified as short-wave cone cells (S-cones) by using the short-wave color opsin-specific antibody, OS-2. Reporter-gene-positive cells of the inner nuclear layer were identified as bipolar cells based on morphological criteria. Transgenes and the endogenous mouse short-wave opsin gene were transcriptionally coactivated at embryonic day 13. These results show that 3.8 or 1.1 kb of human blue opsin upstream flanking sequences are capable of directing expression in short-wave cone cells in a spatially and temporally appropriate fashion and that the human blue opsin gene is the homologue of the short-wave-sensitive pigment, S-opsin, in the short-wave cones of the mouse retina. Expression in the bipolar cells may reflect regulatory mechanisms that are common to these cells and to the cone photoreceptors.