In 1982, Francis Riba, Joao Sanguinheira and Victor Bagoim formed the musical group Os Senhores (The Sirs). A few days later, Joao Sanguinheira friend, the drummer António José, joined the group. When Paulo Santos and To Gonçalves, both guitarists, join the band, the music begins to have a more complex sonority.
In 1984, they change the name to ZEM . On March of 1987 the band recorded their first single "Louca Paixão" (Crazy Passion) and they becomes the first Portuguese group to have a music in the charts of the popular Lisbon radio station Radio Cidade.
In 1987 they participated in the 4th Contest of Rock Rendez-Vous, using the original name again, Os Senhores (The Sirs). They had to change the name, because they already had a record and the regulation of the contest was only allowing the participation of groups without records.
In an interview to the music newspaper Blitz, after the participation in the 4th Contest of Rock Rendez-Vous, Francis Riba confesses what he sees, an black and dark future to the band, since his musical daydreams were taking him to obscure and uncommercial ways.
The debut LP called ZEM was issued in November of 1987. After that, the band was dissolved, due to internal problems..