Early days, White Lion, Zakk Wylde and other projects (1977-2005)
In the late 1970s, he started in a band called "Empty Sky," a rock band with hints of jazz. The band was based out of Brooklyn and was one of the biggest up-and-coming young bands. James was the lead singer and bass guitarist. The band consisted of Robert Littera at lead guitar, Julie Pontecorvo on Trumpet, Marco Lagana on trombone, Frank Bonanno on tenor saxophone, Oscar Olivera on drums, Vincent Chirico on rhythm guitar and John Buccellato on electric piano. The band broke up as the members began to mature and take their separate career paths.
He played bass with Clockwork, his first original hard rock band in 1980 to 1983. He then went on to play in the band Rondinelli with Ray Gillen before joining White Lion in 1984.
He played bass with White Lion from 1984 to 1991, and then went on with White Lion drummer Greg D'Angelo to play with former Kiss guitarist Ace Frehley, and then later with Zakk Wylde's side-project Lynyrd Skynhead who evolved into Pride & Glory and released one album in 1994. Although he left the band during their 1994 tour, he returned to play on Zakk Wylde's 1996 solo album Book of Shadows. He had a brief stint in the recording studio with Ozzy Osbourne in 1994 but the sessions were not used, and Ozzmosis was re-recorded by different musicians the next year. In 1995, James, along with Pride & Glory drummer Brian Tichy joined Slash's Snakepit as touring musicians.He was a member of David Lee Roth's band in the late 1990s and early 2000s and performed on his album Diamond Dave.
In 2004, LoMenzo rejoined Zakk Wylde in his band Black Label Society until October 2005 when he was replaced by Black Label Society's original bassist John DeServio.
From February 10, 2006 up until February 8, 2010, LoMenzo was the bassist of thrash metal band Megadeth. The first Megadeth record he performed on was 2007's United Abominations. LoMenzo also performed on the band's next album, Endgame from 2009. On February 8, 2010, it was announced that original Megadeth bassist Dave Ellefson replaced LoMenzo.
On August 29, 2012, LoMenzo was announced as a cast member of The Amazing Race 21 along with his partner Mark "Abba" Abbattista. They ended up in 6th place out of 11 teams and were the sixth team eliminated at Sokolniki Park in Moscow, Russia due to an unsuccessful search for Abba's stolen passport.
James LoMenzo is best known for his frequent use of the Warwick Buzzard bass and Warwick Stryker bass. His amplification section is dominated by Ashdown amps and cabinets. His effects pedals include Dunlop Crybaby, MXR Chorus, MXR Distortion, and Aphex Punch as well as other pedals. He has his own signature pedal, the Ashdown Lomenzo Hyperdrive. Interestingly, his rig bears a strong resemblance to that of John Entwistle, who also used Ashdown amps and Buzzard basses (which he designed himself). LoMenzo's live rig can be seen here. He is an endorser of RotoSound bass strings. He is also known to play Alembic bass guitar, or more specifically the spyder model. He was also seen playing a Fender Marcus Miller Jazz Bass for the entirety of the 2007 Megadeth Tour of Duty. As of September 2008, James has been seen playing a Yamaha BB Custom Shop model; which in itself, has a slightly smaller body than a standard BB, two pairs of P bass pick-ups (one reversed), a neck pick-up based on a Gibson Model One, a maple neck and a Hipshot D-Tuner.