  The determination of molecular gas masses in star forming dwarf irregular
galaxies is crucial to assess the star formation process in these objects. But
the derivation of the molecular gas content of dwarf galaxies has been a
long-standing problem. CO, as the only practical tracer of cold molecular gas,
has been (and to some extent still is) notoriously diffucult to detect. Yet,
star formation clearly takes place in many dwarf irregulars. This conference
contribution contrasts a number of methods commonly used to derive the
molecular gas contents of dwarf galaxies based on CO observations: Procedures
based on the virial theorem and those relying on radiative transfer arguments.
It is shown that both classes of methods have serious drawbacks. Still,
examples show that there seem to be real differences in the `correct'
conversion factor both between and within star forming dwarf irregular
galaxies.
