When a player reaches the 40 home run level and the 40 stolen base level in the same season, he is said to be a member of the 40-40 club.
For obvious reasons, this club is even more exclusive than the 30-30 club, with only four players achieving this feat in baseball's first 140 years of existence. In fact, it was not until 1988 that such a club even existed, as Jose Canseco cracked 42 home runs and stole 40 bases. Canseco's achievement was tainted somewhat by his admission of steroid use, which also diminished the feats of the next two players to enter the club, Barry Bonds in 1996 (42 HR, 40 SB) and Alex Rodriguez in 1998 (42 HR, 46 SB), as both were implicated in MLB's investigation of steroid use.
The club's fourth member, Alfonso Soriano, hit 46 home runs and stole 41 bases for the Washington Nationals in 2006--a feat that did not receive much publicity due to the Nationals' mediocre record and lack of national prominence. Soriano has never been named in connection with steroid use.