  As part of our ongoing effort to measure exoplanet sizes and transit times
with greater accuracy, we present I band observations of two transits of
OGLE-TR-111b. The photometry has an accuracy of 0.15-0.20% and a cadence of 1-2
minutes. We derive a planetary radius of 1.067 +/- 0.054 Jupiter radii and a
stellar radius of 0.831 +/- 0.031 solar radii. The uncertainties are dominated
by errors in the photometry, rather than by systematic errors arising from
uncertainties in the limb darkening function or the stellar mass. Both the
stellar radius and the planetary radius are in agreement with theoretical
expectations. The transit times are accurate to within 30 seconds, and allow us
to refine the estimate of the mean orbital period: 4.0144479 +/- 0.0000041
days.
