The present invention provides illudin analogs of the general formula I: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 have any of the values defined in the specification, and pharmaceutically acceptable salts thereof, as well as pharmaceutical compositions comprising compounds of formula I, intermediates and processes useful for preparing compounds of formula I, and methods comprising inhibiting tumor growth or treating cancer by administering one or more compounds of formula I.