  We plan to measure the angular diameters of a sample of Penn State-Torun
Planet Search (PTPS) giant exoplanet host star candidates using the Navy
Precision Optical Interferometer. The radii of evolved giant stars obtained
using spectroscopy are usually ill-defined because of the method's indirect
nature and evolutionary model dependency. The star's radius is a critical
parameter used to calculate luminosity and mass, which are often not well known
for giant stars. Therefore, this problem also affects the orbital period, mass,
and surface temperature of the planet. Our interferometric observations will
significantly decrease the errors for these parameters. We present preliminary
results from NPOI observations of six stars in the PTPS sample.
