(Received 14 May 2002; published 24 September 2002)The beam-induced electron cloud buildup is one of the major concerns for the SPS and the design ofthe future LHC. During the 2000 run, this effect has also been observed in the PS with the nominalLHC-type beam. The electron cloud induces a baseline distortion in electrostatic pickup signals, bothduring the last turns in the PS, when the full bunch length is reduced to less than 4 ns, and in the transferline between the PS and the SPS rings. In the year 2001, modifications in the rf hardware allowed us tostudy the properties of the beam instability related with the electron cloud phenomenon for a totalbunch length of about 10 ns. The complete set of experimental observations carried out in the PSmachine is presented and discussed in detail.