Thank you, Marius, for your advice, which worked. Stefan, would it make sense to add something like the following to your documentation? If you have different versions of Python on your machine, the simple command 'pip' will by default look for the version that came with your system. Use a more specific command such as pip3.4 install lxml to install lxml in a particular version of Python on your machine. Look in /usr/local/bin for available versions of the pip installer. There is a bug in Mavericks that may prevent the installation of lxml. As a workaround, run the command export CFLAGS=-Qunused-arguments before running STATIC_DEPS=true pip install lxml For a discussion of the bug see http://bugs.python.org/issue21244 https://github.com/python-imaging/Pillow/issues/527 Martin Mueller Professor emeritus of English and Classics