The band went on to become major stars, and by the early 1980s they were one of the most successful rock acts of the time. 1984 was their most successful album. The lead single, "Jump", became an international hit and their only single to reach number one on the Billboard Hot 100. The following singles, "Panama" and "I'll Wait", both hit number 13 on the U.S. charts. The album went on to sell over 12 million copies in the U.S. alone. In 1985, the band replaced lead singer David Lee Roth with former Montrose lead vocalist Sammy Hagar. With Hagar, the group would release four U.S. number-one albums over the course of 11 years. Hagar left the band in 1996 shortly before the release of the band's first greatest hits collection, Best Of – Volume I. Former Extreme frontman Gary Cherone was quickly recruited as lead singer to replace Hagar, and Van Halen III was released in 1998. Cherone left the band in frustration in 1999 after the tour due to the poor commercial performance of the album.