Hi Ceki. I just migrated an elderly application using log4j and jcl to logback except logback doesn't run under Java 1.4 (which is what I have on this AS/400). Bummer. I wanted the markers to be able to filter on threads. Oh well. I could not locate anywhere on the logback pages that Java 5 is a hard requirement (but it was mentioned way down in a slf4j page). I'd suggest you add a notice to the download page. -- Thorbjørn Ravn Andersen "...plus... Tubular Bells!"