In this study, the effects of aspirin (acetyl salicylic acid-ASA) on the third instar larvae salivary gland polytene chromosomes of Drosophila melanogaster have been investigated. The third instar larvae have been fed on medium containing ASA. In the polytene chromosome slides prepared from this larvae, some chromosomal aberrations, described as ectopic threads between different arms and banding regions were observed. The possible mechanisms of the ectopic pairing caused by ASA have been discussed.