  The open clusters fundamental physical parameters are important tools to
understand the formation and evolution of the Galactic disk and as grounding
tests for star formation and evolution models. However only a small fraction of
the known open clusters in the Milky Way has precise determination of distance,
reddening, age, metallicity, radial velocity and proper motion. One of the
major problems in determining these parameters lies on the difficulty to
separate cluster members from field stars and to assign membership. We propose
a decontamination method by employing 2MASS data in the encircling region of
the clusters NGC1981, NGC2516, NGC6494 and M11. We present a decontaminated CMD
of these objects showing the membership probabilities and structural parameters
as derived from King profile fitting.
