Big Brother 13 was the thirteenth season of the American reality television series Big Brother. It is based upon the Netherlands series of the same name, which gained notoriety in 1999 and 2000. The series premiered on CBS on July 7, 2011 and lasted ten weeks until the live finale on September 14, 2011. The thirteenth season continued to have an increase in ratings, much like the previous two seasons had. The season premiered to a total of 7.89 million viewers, a slight increase from the previous season's launch. The season finale had a total of 7.78 million viewers, only slightly lower than the previous season. In total, the series averaged 7.95 million viewers, higher than that of the previous three seasons and the highest since Big Brother 5 in 2004. Big Brother 13 featured a total of 14 HouseGuests, six of which were previous HouseGuests from past seasons.