Hmmmm... I'm getting there now I think, but I'm not quite there yet! Thanks archdruid and aprilgem. I've spotted that there is a tick box against the JPEG on my save dialog box with "thumbnail" in it, so I reckon archdruids theory about PS saving a thumbnail with the thumbnail :-) is the right one. The only problem is that I can't uncheck it! The check box is enabled but greyed out and no comnination of the other options I seem to have control over affect it. It's a standard JPEG I want to save not a JPEG 2000. There is a SaveForWeb in CS2 aprilgem, and that does seem to work as an option for producing smaller files. So that is the way I'll do it from now on, I think, but I'm still curious about why I'm being forced into saving a thumbnail in the standard dialog box.