Oct factors are members of the POU family of transcription factors that are shown to play important roles during development in mammals. Here we report the cDNA cloning and expression of a Drosophila Oct transcription factor. Whole mount in situ hybridization experiments revealed that the spatial expression patterns of this gene during embryonic development have not yet been observed for any other gene. In early embryogenesis, its transcripts are transiently expressed as a wide uniform band from 20% to 40% of the egg length, very similar to that of gap genes. This pattern progressively resolves into a series of narrower stripes followed by expression in 14 stripes. Subsequently, transcripts from this gene are expressed in the central nervous system and the brain. When expressed in the yeast Saccharomyces cerevisiae, this Drosophila factor functions as a strong, octamer-dependent activator of transcription. Our data strongly suggest possible functions for the Oct factor in pattern formation in Drosophila that might transcend the boundaries of genetically defined segmentation genes.