Contract details aren't known at this time.
Mercilus, who's 6-foot-4 and 254 pounds, was a force at defensive end for Illinois, leading the nation in sacks (16) and forced fumbles (nine). He will be moved to outside linebacker in Houston's 3-4 scheme.
UPDATE: Mercilus' deal will pay him $7.634 million, including $6.55 million guaranteed, according to John McClain of the Houston Chronicle. McClain also reported that Mercilus will receive a $3.99 million signing bonus.