 " The Sixth Extinction " was first shown in the United States on November 7 , 1999 . This episode earned a Nielsen rating of 10 @.@ 6 , with a 16 share , meaning that roughly 10 @.@ 6 percent of all television @-@ equipped households , and 16 percent of households watching television , were tuned in to the episode . It was viewed by 17 @.@ 82 million viewers and was the most watched episode of the seventh season in the United States . The episode aired in the United Kingdom and Ireland on Sky1 on May 7 , 2000 , and received 1 @.@ 00 million viewers and was the third most watched episode that week . Fox promoted the episode with the tagline " Something is driving Mulder insane . Something he 's been searching for . Something he shouldn 't have found . " The episode was later included on The X @-@ Files <unk> , Volume 3 – Colonization , a DVD collection that contains episodes involved with the alien <unk> 's plans to take over the earth . 
