I just released tox-2.1.0 to pypi which streamlines the "passenv" behaviour to accomodate a number of issues, see the changelog below. You can find docs for the virtualenv based test runner here: http://tox.testrun.org have fun, holger 2.1.0 ----- - fix issue258, fix issue248, fix issue253: for non-test commands (installation, venv creation) we pass in the full invocation environment. - remove experimental --set-home option which was hardly used and hackily implemented (if people want home-directory isolation we should figure out a better way to do it, possibly through a plugin) - fix issue259: passenv is now a line-list which allows to intersperse comments. Thanks stefano-m. - allow envlist to be a multi-line list, to intersperse comments and have long envlist settings split more naturally. Thanks Andre Caron. - introduce a TOX_TESTENV_PASSENV setting which is honored when constructing the set of environment variables for test environments. Thanks Marc Abramowitz for pushing in this direction.