Not compressed lossless (I was searching out this for flac files), but I found out this about two recent installs: a Pioneer 800PRS doesn't support *.wav through USB (I didn't pay attention to this when purchasing) and a Pioneer 700BT does support *.wav through USB (again, didn't pay attention). Nice surprise with the 700BT, and it works flawless with a WD 160GB HDD. With *.wav, a little over 200 CD's. Plenty for this cat.