<P> CSI 's theme song was , since the last episode of season one , `` Who Are You '' , written by Pete Townshend with vocals by lead singer Roger Daltrey of The Who . Daltrey made a special appearance in the season - seven episode `` Living Legend '' , which also contained many musical references such as the words `` Who 's next '' on a dry - erase board in the episode 's opening sequence . In certain countries , to avoid music licensing fees , a unique theme was used , instead . </P>
<P> CSI 's theme song was , since the last episode of season one , `` Who Are You '' , written by Pete Townshend with vocals by lead singer Roger Daltrey of The Who . Daltrey made a special appearance in the season - seven episode `` Living Legend '' , which also contained many musical references such as the words `` Who 's next '' on a dry - erase board in the episode 's opening sequence . In certain countries , to avoid music licensing fees , a unique theme was used , instead . </P>
when did csi start using who are you
when did csi start using who are you
the last episode of season one
the last episode of season one