  We present accurate V-band photometry for a planetary transit of OGLE-TR-111
acquired with VIMOS at the ESO Very Large Telescope. The measurement of this
transit allows to refine the planetary radius, obtaining R_p= 1.01 +/- 0.06
R_J. Given the mass of M_p = 0.53 M_J previously measured from radial
velocities, we confirm that the density is rho_p= 0.6 +/- 0.2 g/cm^3. We also
revise the ephemeris for OGLE-TR-111-b, obtaining an accurate orbital period P=
4.014484 +/- 0.000014 days, and predicting that the next observable transits
would occur around December 2006, and after that only in mid-2008. Even though
this period is different from previously published values, we cannot yet rule
out a constant period.
