When running the multiproject plugin, it runs a clean on all sub-projects and then runs the javadoc report. The problem comes up when your project needs to run xdoclet to generate interface classes. Since you are doing the javadoc step before any compile, these xdoclet-generated classes dont show up in the javadoc, and you get a pile of unresolved messages out of the javadoc command. Solution is to do reorder multiproject to do a compile first (and since most people just add xdoclet as a preGoal to compile, xdoclet will be run) - or maybe you define compile as a preGoal to javadoc ?