  A planetary microlensing event occurs when a planet perturbs one of the two
images created in a point-mass microlensing event, causing a deviation from the
standard Paczy\'nski curve. Determination of the two physical parameters that
can be extracted from a planetary microlensing event, the planet/star mass
ratio q, and the planet/star separation in units of the stellar Einstein ring,
$y_p$, is hampered by several types of degeneracies. There are two distinct and
qualitatively different classes of planetary events: major and minor image
perturbations. For major image perturbations, there is a potentially crippling
continuous degeneracy in q which is of order $\delta_d^{-1}$, where $\delta_d$
is the maximum fractional deviation of the planetary perturbation. Since the
threshold of detection is expected to be $\delta_d \sim 5%$, this degeneracy in
q can be a factor of $\sim 20$. For minor image perturbations, the continuous
degeneracy in q is considerably less severe, and is typically less than a
factor 4. We show that these degeneracies can be resolved by observations from
dedicated telescopes on several continents together with optical/infrared
photometry from one of these sites. There also exists a class of discrete
degeneracies. These are typically easy to resolve given good temporal coverage
of the planetary event. Unambiguous interpretation of planetary microlensing
events requires the resolution of both types of degeneracy. We describe the
degeneracies in detail and specify the situations in which they are
problematic. We also describe how individual planet masses and physical
projected separations can be measured.
