Since 1999 Polysics have released several albums. The albums 1st P and A.D.S.R.M! were released on the independent label DECKREC Records. Just after the release of 1st P their bassist, known only as "POLY-2", left. The band dropped the "POLY-X" names, and reduced to a trio, with new member Fumi on Bass Support on some of the tracks from Neu. In 1999, Asian Man Records released their US Debut album, Hey! Bob! My Friend to rave reviews, but weak sales. The album was a compilation of tracks from their first two Japanese releases. In 2000, Polysics signed to Ki/oon Records (a subsidiary of Sony Music Japan Inc.) and released their first major album Neu. The album carried with it the same manic energy as their independent releases but more refined. On the 2001 album Eno, Synthesizers became more prevalent in the mix, but the songs still had an intense punk-like energy. For this album, Fumi returned to the band as a full member, returning Polysics to a quartet. 2002 saw the release of the album For Young Electric Pop, Polysics attempt at a pop album. The manic punk energy was minimized, but the band showed it had an amazing sense of harmony and style. The songs "Black Out Fall Out" and "Code 4" from this album are very emotional.

In 2003, drummer Junichi Sugai left the band after recording the Kaja Kaja Goo EP. For the 2003 album National P, Ishimaru joined on Drum Support, returning Polysics to a trio. Also in 2003, Neu was released on Asian Man Records in the United States to rave reviews and great sales. Polysics went to the US to tour, which was then captured on the PippikkippippiP In USA DVD. In 2004, Polysics released a Best Of compilation titled Polysics or Die!!!! in Europe and the USA. Polysics toured Europe and the US for the 2005 US Release of Polysics or Die!!!!. With the early 2006 release of "Now Is The Time!", they toured the US and the UK, supporting high profile UK artists such as Graham Coxon and the Kaiser Chiefs