Spermatogenesis in both the model object Drosophila melanogaster and mammals, including humans, is characterized by the specificity of the regulation of gene expression at both the transcriptional and translational levels, which is manifested in the existence of testis-specific transport mRNA receptors, NXF (nuclear export factor). By using antibodies to the C-terminal part of the Dm NXF1 protein (SBR), a considerable amount of this protein is found to be present at all stages of spermatogenesis. At early stages of spermatogenesis, we have shown the cytoplasmic localization of the Dm NXF1 protein. This protein is located in the nucleus or in the nuclear envelope at the stage of rounded spermatids. During spermatid elongation, the Dm NXF1 protein is located polarly and disposed only along one side of the extended spermatid nucleus, while, at the stage of spermatid individualization, it is translocated into the spermatozoan tail in the form of large cytoplasmic granules.