gentle persons, the above error appears if the requiered libraries from Qt/MAC are NOT installed (!). As explained in the included Readme of xdrawchem (and displayed by the xdrawchem installer) you need to install these libraries. A binary installer is available at http://naranja.umh.es/~macqt/installer/QtMac-Installer.dmg.gz (see the included readme for defining the path variables). If you like to compile these libraries by yourself, visit www.trolltech.com at http://www.trolltech.com/download/qt/mac.html