Thanks, Dieter. The FTP script basically walks the source folder tree on the Zope side and issues a 'mget *' instruction in each folder, then either issues a 'cd name' to visit an enclosed folder or a 'cdup' to return to a previous folder. There is only one FTP instance at work (Zope at the source end, wu-ftp at the sink end). I would have thought that FTP would be dumb and not fire off independent copy processes for each transfer. I'll try it again and take a look using lsof.