We have characterized the phenomenon of super-unstability in yellow and scute loci of Drosophila melanogaster. A few derivatives with different combinations of yellow and scute phenotypes appeared after dysgenic cross between potentially super-unstable stock y2nsscme and P[ry+, (delta 2-3)] (99B). Essentially, the double alterations of yellow and scute phenotypes constitute more than 40% of all derivatives. Most frequently the mutations in both yellow and scute loci change coordinately giving rise to the y+nssc+ allele. Lethal derivatives were not observed. The spectrum and the frequency of the y2nsscme mutagenesis in females differ considerably from the analogous in males. Possibly, the neutral homologous chromosome in females changes contacts between two insertions, and because of that mutagenesis changes too. Thus, all alterations in the double super-unstable system seem to be connected with the recombination between two unstable insertions A genetic exchange may by initiated by a double-strand breaks induced by the transposase of the ends of insertions.