With the help of in situ hybridization respective location of 33 microclones from the genomic library of the Drosophila melanogaster large band 10A1-2, 4 clones obtained by chromosomal walking and 18 chromosomal rearrangements with breakpoints in the limits of this band was determined. A DNA fragment homologous to poly(A)+ RNA from the 3rd instar larvae has been revealed. Summarizing the obtained and published data, at least 3 genes and 6 transcriptionally active fragments appear to be located in the 10A1-2 band. Using DNA clones from different regions of Drosophila melanogaster 10A1-2 as probes in some Diptera species, the 10A1-2 distal clone, carrying vermilion gene, in D. virilis was shown to be located in a very thin band of the 5A region, while the proximal clones of the 10A1-2 band were mapped in a large band of the 2B region. In D. paranaensis a sequence homologous to the vermilion gene DNA was mapped in a large band, whereas the proximal clones of the 10A1-2 band were localized in a different region. These results evidence for the fact that DNA sequences are not evolutionary fixed, i. e. in different species they may belong to different chromomeres.