Genetic instability in Strepfomyces ambofaciens DSM 40697 involves genomic rearrangements such as amplifications and deletions of particular DNA sequences. Most amplifications were located in two amplifiable regions, one of which, called AUD6 (amplifiable unit of DNA no. 6) was revealed to be a rearrangement hotspot. Indeed, 30% of the mutant strains studied had amplifications, deletions or both at the AUD6 locus. This locus contains several reiterations which are specific to this AUD. Moreover, one of the endpoints of the AUD6 shows homology with an internal sequence. Deletions occurred exclusively at one side of the amplified DNA sequence (ADS) and removed part of the proximal copy of this ADS, leading to the conclusion that multiple rearrangements can occur at this AUD locus.