[en] The accelerator complex at DESY consists of a number of linear and circular accelerators for acceleration and storage of electrons, positrons and protons. Most of the accelerators are used for the injection scheme of the proton-electron/positron collider HERA. The protons are injected into the proton synchrotron DESY III with a momentum of 310 MeV/c. They are bunched and accelerated to 7.5 GeV/c within 2 s. 8 fills of DESY III can be accumulated in PETRA II, resulting in 70 bunches and a design current of 150 mA. They are accelerated up to 40 GeV/c within 2.5 minutes and injected into HERAp. HERAp can accumulate 200 bunches. The acceleration to 820 GeV/c takes about 30 minutes where the lifetime of the proton beam is a few hundred hours. The electrons/positrons are injected with an energy of 450 MeV from the LINAC II and the intensity accumulator PIA into the electron synchrotron DESY II. They leave the synchrotron with an energy of 7 GeV into PETRA II which accelerates them up to 12 GeV. After injection into HERAe the electrons are accelerated up to 30 GeV and stored for a few hours. The counterrotating electron and proton beams collide head on in three interaction points. To achieve a high luminosity in the HERA ep collider, it is necessary to control the emittance of the proton beam through the entire chain of preaccelerators while the electron beam has its natural emittance. This paper concentrates on the transverse emittance of the proton beam through the chain of proton accelerators DESY III, PETRA II and HERAp. The performance of the profile monitors used in the accelerators is discussed and the different types are compared. Also results of the emittance behavior in the accelerators are presented. (J.P.N.)