This thesis is concerned with the effect of widespread internet use on the sales of audio CDs. It analyses trends in the American and Czech markets from the end of the 1990's to today. Its analysis is based on the relationship between musical genres and their respective target audiences with the hypothesis being that genres with listeners who have adopted the internet more rapidly are more affected than other genres. The thesis proves that the decrease in music sales in the last ten years, the bulk of which have been CDs, has been caused by the graudual establishment of the internet with its probable illegal downloading of recordings and the change in format to MP3 from CD.