  We present a K survey of 29 fields covering approximately 90 arcmin^2 from
the Medium Deep Survey (MDS) catalogue down to a completeness magnitude of
K=18.0 (limiting magnitude K=19.0). The morphology obtained by the MDS team
using high resolution images from HST/WFPC2 along with our NIR observations
allow a Colour-Magnitude and Colour-Colour analysis that agrees in general with
spectral evolution models (Bruzual & Charlot 1998) especially if a reasonable
range of metallicities for the Simple Stellar Populations used (0.2 < Z/Zsolar
< 2.5) is considered. However, a significant population of spheroids was found,
which appear bluer than expected, confirming previous observations (Forbes et
al. 1996, Koo et al. 1996, Glazebrook et al. 1998). This blueness might
possibly signal the existence of non-negligible star formation in ellipticals
and bulges at medium redshift. A number counts calculation for different
morphological types show disks become the dominant population at faint
magnitudes. The median redshift of the sample is z~0.2, from a photometric
redshift estimation using V-K and I-K. A search for EROs in the survey field
was also performed, with no detection of objects having I-K > 4.5, setting an
upper limit to the number density of EROs at dn_{EROs}/d\Omega < 0.011
arcmin^{-2} (K < 18.0).
